Sources of pollution are numerous and varied in nature. There are natural and anthropogenic air pollution. Natural pollution occurs, as a rule, as a result of natural processes beyond any human influence, and anthropogenic pollution occurs as a result of human activity.
Natural air pollution is caused by the influx of volcanic ash, cosmic dust (up to 150-165 thousand tons annually), plant pollen, sea salts, etc. The main sources of natural dust are deserts, volcanoes and bare areas of land.
Anthropogenic sources of air pollution include power plants burning fossil fuels, industrial enterprises, transport, and agricultural production. Of the total amount of pollutants emitted into the atmosphere, about 90% are gaseous substances and about 10% are particles, i.e. solid or liquid substances.
There are three main anthropogenic sources of air pollution: industry, domestic boiler houses, and transport. The contribution of each of these sources to total air pollution varies greatly depending on location.
In the last decade, the supply of pollutants from individual industries and transport has been distributed in the order shown in the table:
Main pollutants
Air pollution is the result of emissions of pollutants from various sources. The cause-and-effect relationships of this phenomenon must be sought in the nature of the earth's atmosphere. Thus, pollutants are transported through the air from sources of occurrence to places of their destructive impact; in the atmosphere they can undergo changes, including the chemical transformation of some pollutants into other, even more dangerous substances.
Atmospheric pollutants are divided into primary, which enter directly into the atmosphere, and secondary, which are the result of the transformation of the latter. The main harmful impurities of pyrogenic origin are the following:
a) Carbon monoxide. It is produced by incomplete combustion of carbonaceous substances. It enters the air as a result of the combustion of solid waste, exhaust gases and emissions from industrial enterprises. Every year, at least 1250 million tons of this gas enter the atmosphere. Carbon monoxide is a compound that actively reacts with components of the atmosphere and contributes to an increase in temperature on the planet and the creation of a greenhouse effect.
b) Sulfur dioxide. Released during the combustion of sulfur-containing fuel or processing of sulfur ores.
c) Sulfuric anhydride. Formed by the oxidation of sulfur dioxide. The final product of the reaction is an aerosol or solution of sulfuric acid in rainwater, which acidifies the soil and aggravates diseases of the human respiratory tract. The fallout of sulfuric acid aerosol from smoke flares of chemical plants is observed under low clouds and high air humidity. Leaf blades of plants growing at a distance of less than 11 km. from such enterprises are usually densely dotted with small necrotic spots formed in places where drops of sulfuric acid settled.
d) Hydrogen sulfide and carbon disulfide. They enter the atmosphere separately or together with other sulfur compounds. The main sources of emissions are enterprises producing artificial fiber, sugar, coke plants, oil refineries, and oil fields.
e) Nitrogen oxides. The main sources of emissions are enterprises producing nitrogen fertilizers, nitric acid and nitrates, and aniline dyes.
f) Fluorine compounds. Fluorine-containing substances enter the atmosphere in the form of gaseous compounds - hydrogen fluoride or sodium and calcium fluoride dust. The compounds are characterized by a toxic effect. Fluorine derivatives are strong insecticides.
g) Chlorine compounds. They come into the atmosphere from chemical plants producing hydrochloric acid. In the atmosphere they are found as impurities of chlorine molecules and hydrochloric acid vapors.
Consequences of pollution
a) Greenhouse effect.
The Earth's climate, which depends mainly on the state of its atmosphere, has changed periodically throughout geological history: periods of significant cooling alternated, when large areas were covered with glaciers, and periods of warming. But lately, meteorologists have been sounding the alarm: the Earth's atmosphere appears to be warming up much faster than at any time in the past. This is due to human activity, which, firstly, heats the atmosphere by burning large amounts of coal, oil, gas, as well as the operation of nuclear power plants. Secondly, and this is most important, the burning of fossil fuels, as well as the destruction of forests, leads to the accumulation of large amounts of carbon dioxide in the atmosphere. Over the past 120 years, the content of this gas in the air has increased by 17%. In the earth's atmosphere, carbon dioxide acts like glass in a greenhouse: it freely transmits the sun's rays to the Earth's surface, but retains the heat of the Earth's surface heated by the Sun. This causes the atmosphere to warm up, known as the greenhouse effect. According to scientists, in the coming decades the average annual temperature on Earth due to the greenhouse effect may increase by 1.5-2 C.
The problem of climate change as a result of greenhouse gas emissions should be considered as one of the most important modern problems associated with long-term impacts on the environment, and it should be considered in conjunction with other problems caused by anthropogenic impacts on nature.
b) Acid rain.
Oxides of sulfur and nitrogen, which are released into the atmosphere due to the operation of thermal power plants and automobile engines, combine with atmospheric moisture and form small droplets of sulfuric and nitric acids, which are carried by winds in the form of acid fog and fall to the ground as acid rain. These rains have an extremely harmful effect on the environment:
the yield of most agricultural crops decreases due to damage to foliage by acids;
calcium, potassium, magnesium are washed out of the soil, which causes degradation of fauna and flora;
forests are dying;
the water of lakes and ponds is poisoned, where fish die and insects disappear;
waterfowl and animals that feed on insects are disappearing;
forests are dying in mountainous areas, causing mudflows;
the destruction of architectural monuments and residential buildings is accelerating;
the number of human diseases is increasing.
Photochemical fog (smog) is a multicomponent mixture of gases and aerosol particles of primary and secondary origin.
Research by scientists shows that smog occurs as a result of complex photochemical reactions in air polluted with hydrocarbons, dust, soot and nitrogen oxides under the influence of sunlight, elevated temperatures of the lower layers of air and large amounts of ozone. In dry, polluted and warm air, a transparent bluish fog appears, which smells unpleasant, irritates the eyes, throat, causes suffocation, bronchial asthma, and emphysema. The foliage on the trees withers, becomes spotted, and turns yellow.
Smog is a common phenomenon over London, Paris, Los Angeles, New York and other cities in Europe and America. Due to their physiological effects on the human body, they are extremely dangerous for the respiratory and circulatory systems and often cause premature death in urban residents with poor health.
d) Ozone hole in the atmosphere.
At an altitude of 20-50 km, the air contains an increased amount of ozone. Ozone is formed in the stratosphere due to molecules of ordinary, diatomic oxygen O2, which absorbs hard UV radiation. Recently, scientists have become extremely concerned about the decline in ozone levels in the ozone layer of the atmosphere. A “hole” was discovered in this layer over Antarctica, where its content is less than usual. The ozone hole has caused an increase in the UV background in countries located in the Southern Hemisphere, primarily in New Zealand. Doctors in this country are sounding the alarm, noting a significant increase in the number of diseases caused by increased UV radiation, such as skin cancer and eye cataracts.
Air protection
Air protection includes a set of technical and administrative measures directly or indirectly aimed at stopping or at least reducing the increasing air pollution resulting from industrial development.
Territorial and technological problems include both the location of sources of air pollution and the limitation or elimination of a number of negative effects. The search for optimal solutions to limit air pollution from this source has intensified in parallel with the growing level of technical knowledge and industrial development - a number of special measures have been developed to protect the air environment.
Protection of the atmosphere cannot be successful with unilateral and half-hearted measures directed against specific sources of pollution. The best results can be obtained only with an objective, multilateral approach to determining the causes of air pollution, the contribution of individual sources and identifying real opportunities to limit these emissions.
Many modern man-made substances, when released into the atmosphere, pose a significant threat to human life. They cause great damage to human health and wildlife. Some of these substances can be carried over long distances by winds. For them there are no state borders, as a result of which this problem is international.
In urban and industrial conglomerates, where there are significant concentrations of small and large sources of pollutants, only an integrated approach, based on specific restrictions for specific sources or their groups, can lead to the establishment of an acceptable level of air pollution under a combination of optimal economic and technological conditions. Based on these provisions, an independent source of information is needed that would have information not only on the degree of air pollution, but also on the types of technological and administrative measures. An objective assessment of the state of the atmosphere, coupled with information about all emission reduction opportunities, allows for the creation of realistic plans and long-term forecasts of air pollution for worst-case and best-case scenarios and forms a solid basis for developing and strengthening an air protection program.
By duration, atmosphere protection programs are divided into long-term, medium-term and short-term; Methods for preparing air environmental protection plans are based on conventional planning methods and are coordinated to meet long-term requirements in this area.
The most important factor in forming forecasts for atmospheric protection is the quantitative assessment of future emissions. Based on an analysis of the sources of emissions in individual industrial areas, especially from combustion processes, a nationwide assessment of the main sources of solid and gaseous emissions over the past 10-14 years has been established. Then a forecast is made about the possible level of emissions for the next 10-15 years. At the same time, two directions of development of the national economy were taken into account: 1) pessimistic assessment - the assumption of maintaining the existing level of technology and emission restrictions, as well as maintaining existing methods of pollution control at existing sources. 2) optimistic assessment - the assumption of maximum development and use of new technology with a limited amount of waste and the use of methods that reduce solid and gaseous emissions from both existing and new sources. Thus, an optimistic estimate becomes the goal when reducing emissions.
The degree of harmfulness of environmental pollutants depends on many environmental factors and on the substances themselves. Scientific and technological progress poses the task of developing objective and universal criteria for harmfulness. This fundamental problem of protecting the biosphere has not yet been completely resolved.
Individual areas of research on atmospheric protection are often grouped into a list according to the rank of processes leading to air pollution.
1. Sources of emissions (location of sources, raw materials used and methods of their processing, as well as technological processes).
2. Collection and accumulation of pollutants (solid, liquid and gaseous).
3. Determination and control of emissions (methods, instruments, technologies).
4. Atmospheric processes (distance from chimneys, long-distance transport, chemical transformations of pollutants in the atmosphere, calculation of expected pollution and forecasting, optimization of chimney heights).
5. Recording of emissions (methods, instruments, stationary and mobile measurements, measurement points, measurement grids).
6. Impact of polluted atmosphere on people, animals, plants, buildings, materials, etc.
7. Comprehensive air protection combined with environmental protection.
Atmospheric protection methods
1. Legislative. The most important thing in ensuring a normal process for the protection of atmospheric air is the adoption of an appropriate legislative framework that would stimulate and assist in this difficult process. However, in Russia, no matter how sad it may sound, in recent years there has been no significant progress in this area. The world already experienced the latest pollution that we are now facing 30-40 years ago and took protective measures, so we do not need to reinvent the wheel. The experience of developed countries should be used and laws should be passed that limit pollution, provide government subsidies to manufacturers of environmentally friendly cars and benefits to owners of such cars.
In the United States, a law to prevent further air pollution came into force in 1998.
In general, in Russia there is practically no normal legislative framework that would regulate environmental relations and stimulate environmental protection measures.
2. Architectural planning. These measures are aimed at regulating the construction of enterprises, planning urban development taking into account environmental considerations, greening cities, etc. When constructing enterprises, it is necessary to adhere to the rules established by law and prevent the construction of hazardous industries within the city limits. It is necessary to carry out mass greening of cities, because green spaces absorb many harmful substances from the air and help cleanse the atmosphere. Unfortunately, in the modern period in Russia, green spaces are not so much increasing as decreasing. Not to mention the fact that the “dormitory areas” built in their time do not stand up to any criticism. Since in these areas, houses of the same type are located too densely (to save space) and the air between them is subject to stagnation.
The problem of rational layout of the road network in cities, as well as the quality of the roads themselves, is also extremely acute. It is no secret that the roads thoughtlessly built in their time were not at all designed for the modern number of cars. It is also impossible to allow combustion processes in various landfills, since in this case a large amount of harmful substances are released with smoke.
3. Technological and sanitary-technical. The following activities can be distinguished: rationalization of fuel combustion processes; improving the sealing of factory equipment; installation of high pipes; massive use of treatment devices, etc. It should be noted that the level of treatment facilities in Russia is at a primitive level; many enterprises do not have them at all, and this despite the harmfulness of the emissions from these enterprises.
Many production facilities require immediate reconstruction and re-equipment. An important task is also to convert various boiler houses and thermal power plants to gas fuel. With such a transition, emissions of soot and hydrocarbons into the atmosphere are greatly reduced, not to mention the economic benefits.
An equally important task is to educate Russians about environmental consciousness. The lack of treatment facilities can, of course, be explained by a lack of money (and there is a lot of truth in this), but even if there is money, they prefer to spend it on anything but the environment. The lack of elementary ecological thinking is especially noticeable at the present time. If in the West there are programs through the implementation of which the foundations of environmental thinking are laid in children from childhood, then in Russia there has not yet been significant progress in this area.
The main air pollutant is transport powered by heat engines. Car exhaust gases produce the bulk of lead, nitrogen oxide, carbon monoxide, etc.; tire wear - zinc; diesel engines - cadmium. Heavy metals are strong toxicants. Each car emits more than 3 kg of harmful substances daily. Gasoline, obtained from certain types of oil and petroleum products, releases sulfur dioxide into the atmosphere when burned. Once in the air, it combines with water and forms sulfuric acid. Sulfur dioxide is the most toxic, it affects the human lungs. Carbon monoxide or carbon monoxide, entering the lungs, combines with hemoglobin in the blood and causes poisoning of the body. In small doses, acting systematically, carbon monoxide promotes the deposition of lipids on the walls of blood vessels. If these are the vessels of the heart, then the person develops hypertension and may have a heart attack, and if these are the vessels of the brain, then the person has the potential to have a stroke. Nitrogen oxides cause swelling of the respiratory system. Zinc compounds not only affect the nervous system, but also, accumulating in the body, cause mutations.
The main directions of work in the field of protecting the atmosphere from pollution by vehicle emissions are: a) creation and expansion of production of cars with highly economical and low-toxic engines, including further dieselization of cars; b) development of work on the creation and implementation of effective exhaust gas neutralization systems; c) reducing the toxicity of motor fuels; d) development of work on the rational organization of vehicle traffic in cities, improving road construction in order to ensure non-stop traffic on highways.
Currently, the planet's automobile fleet amounts to more than 900 million vehicles. Therefore, even a slight reduction in harmful emissions from cars will significantly help the environment. This direction includes the following activities.
Adjusting the fuel and brake systems of the car. Fuel combustion must be complete. This is facilitated by filtration, which allows the gasoline to be cleared of clogging. A magnetic ring on the gas tank will help catch metal contaminants in the fuel. All this reduces the toxicity of emissions by 3-5 times.
Air pollution can be significantly reduced by maintaining optimal driving habits. The most environmentally friendly operating mode is movement at a constant speed.
Dust from industrial enterprises, containing mainly metal particles, poses a great health hazard. Thus, dust from copper smelters contains iron oxide, sulfur, quartz, arsenic, antimony, bismuth, lead or their compounds.
In recent years, photochemical fogs have begun to appear, resulting from the exposure of vehicle exhaust gases to intense ultraviolet radiation. A study of the atmosphere made it possible to establish that the air even at an altitude of 11 km is polluted by emissions from industrial enterprises.
The difficulties of purifying gases from pollutants include, first of all, the fact that the volumes of industrial gases emitted into the atmosphere are enormous. For example, a large thermal power plant is capable of releasing up to 1 billion cubic meters into the atmosphere in one hour. meters of gases. Therefore, even with a very high degree of purification of exhaust gases, the amount of pollutant entering the air basin will be estimated to be significant.
In addition, there is no single universal treatment method for all contaminants. An effective method for purifying waste gases of one pollutant may not be effective for other pollutants. Or a method that has worked well under specific conditions (for example, within strictly limited limits of changes in concentration or temperature) turns out to be ineffective under other conditions. For this reason, it is necessary to use combined methods, combining several methods at the same time. All this determines the high cost of treatment facilities and reduces their reliability during operation.
The World Health Organization, depending on the observed effects, has defined four levels of pollutant concentrations for health indicators:
Level 1 - no direct or indirect effect on a living organism is detected;
Level 2 - sensory irritation, harmful effects on vegetation, reduced atmospheric visibility or other adverse effects on the environment are observed;
Level 3 - there may be either a disorder of vital physiological functions, or changes that lead to chronic diseases or premature death;
Level 4 - acute illness or premature death is possible in the most vulnerable groups of the population.
Harmful impurities in exhaust gases can be presented either in the form of aerosols, or in a gaseous or vaporous state. In the first case, the purification task is to extract suspended solid and liquid impurities contained in industrial gases - dust, smoke, fog droplets and splashes. In the second case - neutralization of gas and vapor impurities.
Cleaning from aerosols is carried out using electric precipitators, filtration methods through various porous materials, gravitational or inertial separation, and wet cleaning methods.
Purification of emissions from gas and vapor impurities is carried out by adsorption, absorption and chemical methods. The main advantage of chemical cleaning methods is a high degree of purification.
The main methods for cleaning emissions into the atmosphere:
Neutralization of emissions by converting toxic impurities contained in the gas stream into less toxic or even harmless substances is a chemical method;
Absorption of harmful gases and particles by the entire mass of a special substance called an absorbent. Typically, gases are absorbed by a liquid, mostly water or suitable solutions. To do this, they use passing through a dust collector operating on the principle of wet cleaning, or spraying water into small drops in so-called scrubbers, where water, sprayed into drops and settling, absorbs gases.
Purification of gases with adsorbents - bodies with a large internal or external surface. These include various brands of active carbons, silica gel, and aluminum gel.
To purify the gas stream, oxidative processes, as well as catalytic transformation processes, are used.
Electric precipitators are used to clean gases and air from dust. They are a hollow chamber containing electrode systems. The electric field attracts small particles of dust and soot, as well as pollutant ions.
The combination of various methods of air purification from pollutants makes it possible to achieve the effect of purifying industrial gaseous and solid emissions.
Ambient air quality control
The problem of air pollution in cities and the general deterioration of air quality is a serious concern. To assess the level of air pollution in 506 cities of Russia, a network of posts of a national service for observing and monitoring air pollution as part of the natural environment has been created. The network determines the content in the atmosphere of various harmful substances coming from anthropogenic sources of emissions. Observations are carried out by employees of local organizations of the State Committee for Hydrometeorology, the State Committee for Ecology, the State Sanitary and Epidemiological Supervision, sanitary and industrial laboratories of various enterprises. In some cities, surveillance is carried out simultaneously by all departments.
The main value of environmental regulation of the content of harmful substances in the air is the maximum permissible concentration, /MPC/. MPC is the content of a harmful substance in the environment that, with constant contact or exposure over a certain period of time, has virtually no effect on human health and does not cause adverse consequences in his offspring. When determining the maximum permissible concentration, not only the impact of harmful substances on human health is taken into account, but also their impact on vegetation, animals, microorganisms, climate, atmospheric transparency, as well as on natural communities as a whole.
Air quality control in populated areas is organized in accordance with GOST “Nature Conservation. Atmosphere. Rules for monitoring air quality in populated areas,” for which three categories of air pollution observation posts are established: stationary, route, mobile or flare. Stationary posts are designed to provide continuous monitoring of the content of pollutants or regular air sampling for subsequent monitoring; for this purpose, stationary pavilions equipped with equipment for conducting regular observations of the level of air pollution are installed in various areas of the city. Regular observations are also carried out at route posts, using vehicles equipped for this purpose. Observations at stationary and route posts at various points in the city make it possible to monitor the level of air pollution. In each city, the concentrations of the main pollutants are determined, i.e. those emitted into the atmosphere by almost all sources: dust, sulfur oxides, nitrogen oxides, carbon monoxide, etc. In addition, the concentrations of substances that are most characteristic of emissions from enterprises in a given city are measured, for example, in Barnaul - these are dust, sulfur and nitrogen dioxides , carbon monoxide, hydrogen sulfide, carbon disulfide, phenol, formaldehyde, soot and other substances. To study the characteristics of air pollution from emissions of individual industrial enterprises, concentration measurements are carried out on the leeward side under the smoke plume emerging from the chimneys of the enterprise at different distances from it. Under-flare observations are carried out on a vehicle or at stationary posts. In order to become more familiar with the characteristics of air pollution created by cars, special surveys are carried out near highways.
Conclusion
The main task of humanity in the modern period is to fully understand the importance of environmental problems and radically solve them in a short time. Human impact on the environment has reached alarming proportions. To fundamentally improve the situation, targeted and thoughtful actions will be needed. A responsible and effective policy towards the environment will be possible only if we accumulate reliable data on the current state of the environment, reasonable knowledge about the interaction of important environmental factors, and if we develop new methods for reducing and preventing harm caused to Nature by humans.
The atmosphere plays an important role in all natural processes. It serves as reliable protection from harmful cosmic radiation and determines the climate of a given area and the planet as a whole.
Drawing a conclusion, it can be noted that atmospheric air is one of the main vital elements of the environment, its life-giving source. Taking care of it, keeping it clean means preserving life on Earth.
Calculation part
Task 1. Calculation of general lighting
1. Determine the category and subcategory of visual work, lighting standards in the workplace, using the data of the option (Table 3) and lighting standards (see Table 1).
3. Distribute general lighting fixtures with LL across the area of the production premises.
5. Determine the luminous flux of a group of lamps in a general lighting system using the data of the option and formula (2).
6. Select a lamp according to the data in the table. 2 and check the fulfillment of the condition of compliance between Fl.table and Fl.calc.
7. Determine the power consumed by the lighting installation.
Table 1. Initial data
Level and sublevel of visual work
S=36*12=432 m2
L=1.75*H=1.75*5=8.75 m
= = 16 lamps
Fl.calc. = (0.9..1.2) => 1554 = (1398..1868) = 1450 - LDC 30
P= pNn= 30*16*4=1920 W
Answer: Fl.calc. = 1450 - LDC 30, R = 1920 W
Task 2. Calculation of noise levels in residential buildings
1. In accordance with the data of the option, determine the reduction in the sound level at the design point and, knowing the sound level from vehicles (noise source), use formula (1) to find the sound level in a residential area.
2. Having determined the sound level in a residential building, draw a conclusion about the compliance of the calculated data with acceptable standards.
Table 1. Initial data
| Option | rn , m | δ, m | W , m | L i.sh., dBA |
| 08 | 115 | 5 | 16 | 75 |
1) Reducing the sound level from its dispersion in space
ΔLс=10 lg (rn/r0)
ΔLс=10 lg(115/7.5)=10lg(15.33)=11.86 dBA
2) Decrease in sound level due to its attenuation in air
ΔLair = (αair *rn)/100
ΔLair =(0.5*115)/100=0.575 dBA
3) Reducing sound levels by green spaces
ΔLgreen = αgreen * V
ΔLgreen =0.5*10=1 dBA
4) Reduction of sound level by the screen (building) ΔLe
ΔLЗЗ =k*w=0.85*16=13.6 dBA
Lрт =75-11.86-0.575-1-13.6-18.4=29.57
Lрт =29.57< 45 - допустимо
Answer:<45 допустимо
Task 3. Assessing the impact of harmful substances contained in the air
1. Rewrite the form of the table. 1 on a blank sheet of paper.
2. Using the regulatory and technical documentation (Table 2), fill out columns 4...8 of Table 1
3. Having chosen the task option (Table 3), fill out columns 1...3 of Table 1.
4. Compare the concentrations of substances specified according to the option (see Table 3) with the maximum permissible (see Table 2) and draw a conclusion about compliance with the standards for the content of each substance in columns 9...11 (see Table 1), i.e.<ПДК, >MPC, = MPC, indicating compliance with standards with a “+” sign, and non-compliance with a “-” sign (see sample).
Table 1. Initial data
Table 2.
| Option | Substance | Concentration of harmful substance, mg/m3 | Hazard Class | Features of the impact | Compliance with the standards of each substance separately | |||||
| actual | maximum permissible | in the air of the working area | in the air of populated areas during exposure time |
|||||||
| in the air of the working area | in the air of populated areas | |||||||||
| maximum one-time | daily average | |||||||||
| <=30 мин | >30 min | £30 min | >30 min | |||||||
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 |
| 01 | Ammonia | 0,5 | 20 | 0,2 | 0,04 | IV | - | <ПДК(+) | >MPC(-) | >MPC(-) |
| 02 | Nitrogen dioxide | 1 | 2 | 0,085 | 0,04 | II | ABOUT* | <ПДК(+) | >MPC(-) | >MPC(-) |
| 03 | Tungsten anhydride | 5 | 6 | - | 0,15 | III | f | <ПДК(+) | >MPC(-) | >MPC(-) |
| 04 | Chromium oxide | 0,2 | 1 | - | - | III | A | <ПДК(+) | >MPC(-) | >MPC(-) |
| 05 | Ozone | 0,001 | 0,1 | 0,16 | 0,03 | I | <ПДК(+) | <ПДК(+) | <ПДК(+) | |
| 06 | Dichloroethane | 5 | 10 | 3 | 1 | II | - | <ПДК(+) | >MPC(-) | >MPC(-) |
Answer: The concentration of harmful substances contained in the air of a working area is permissible, but in the air of populated areas is not permissible.
Task 4. Assessing the quality of drinking water
C1/MPC1 + C2/MPC2 + … + Cn/MPCn
1. Manganese (MPC> Actual concentration) – 0.1>0.04
2. Sulfates (MPC > Actual concentration) – 500 > 50
3. Lithium (MPC> Actual concentration) – 0.03>0.01
4. Nitrites (MPC> Actual concentration) - 3.3< 3,5
5. Formaldehyde (MPC> Actual concentration) – 0.05>0.03
Since class 2 harmful substances are present in water, it is necessary to calculate the sum of the ratios of the concentrations of each substance in a water body to the corresponding MAC values and it should not exceed one.
3,5/3,3+0,03/0,05+0,01/0,03=1,99
Answer: Water contains the harmful substance Nitrites in greater quantities than the established amount; because the water contains substances of hazard class 2, the quality of drinking water was assessed; the sum of the concentration ratios exceeds 1, so the water is not suitable for consumption
Task 5. Calculation of required air exchange during general ventilation
Table 1 – Initial data
For calculations take t beat = 26 °C; t pr = 22 °C, q pr = 0.3 MPC.
1. Select and record the initial data of the option in the report (see Table 1).
2. Perform calculations for the option.
3. Determine the required air exchange.
4. Compare the calculated air exchange rate with the recommended one and draw the appropriate conclusion.
Qizb = Qe.o. +Qp
Qp = n * kp = 200 * 400 = 80000 kJ/h
Qe.o = 3528 * 0.25 * 170 = 149940 kJ/h
Qiz = 80000 * 149940 = 229940 kJ/h
K = L/Vc =38632.4/33600 =1.15
The air exchange rate K=1.15 is suitable for machine and instrument making shops.
Answer: Required air exchange m3/h, air exchange rate K=1.15
Bibliography
1. Life safety. (Textbook) Ed. E.A. Arustamova 2006, 10th ed., 476 p.
2 Fundamentals of life safety. (Tutorial) Alekseev V.S., Ivanyukov M.I. 2007, 240 p.
3. Bolbas M.M. Fundamentals of industrial ecology. - M.: Higher School, 1993.
4. Ecology and life safety. (Tutorial) Krivoshein D.A., Ant L.A. et al. 2000, 447p.
5. Chuikova L.Yu. General ecology. - M., 1996.
6.Life safety. Lecture notes. Alekseev V.S., Zhidkova O.I., Tkachenko N.V. (2008, 160 pp.)
Air protection is one of the most pressing problems of environmental protection. Protecting the atmosphere from pollution from industrial and transport emissions is the most important social task, part of the complex of tasks of the global problem of nature conservation and improving the use of natural resources. Air pollution with harmful substances causes significant material damage to the national economy and leads to an increase in morbidity among the population.
Problems of atmospheric protection constitute a broad area at the intersection of sciences. It includes both general problems of chemical technology, energy, physics and mechanical engineering, as well as issues that are dealt with by doctors, hygienists, etc.
The most effective method of protecting the atmosphere from pollution by harmful substances is the development of new low-waste, resource- and energy-saving technological processes with closed production cycles. However, these issues require large financial costs and the development of new modern technologies and materials. Therefore, without postponing the solution of these issues to the future, at the present stage for most industrial and transport enterprises, cleaning the air emitted into the atmosphere remains the main measure to protect the air basin from pollution.
Of the total mass of air pollutants,
coming from anthropogenic sources, about 90% are various gaseous substances, and 10% are solid and liquid substances.
Suspended substances in the air are called aerosols, which are usually divided into three classes: dust, smoke and mists.
Dusts are polydisperse systems of solid suspended particles ranging in size from 5 to 100 microns.
Fumes are aerosols with particle sizes from 0.1 to 5 microns.
Fogs are liquid aerosols consisting of liquid droplets. They may contain dissolved substances or solid particles. They are formed as a result of condensation of steam or spraying of liquids. The particle size in the first case is close to smoke, and in the second - to dust.
A special place is occupied by soot and ash formed during the combustion of fuel.
Soot is a toxic highly dispersed powder, 95% consisting of carbon particles.
Ash is an unburned fuel residue consisting of mineral impurities.
In dust collection and gas purification technology, the dispersed composition of dust is of decisive importance, since depending on this, the appropriate dust collection equipment is selected.
The most typical gaseous air pollution includes:
sulfur dioxide ( SO 2 ),
carbon monoxide ( CO),
nitrogen oxides and dioxides ( NO, NO 2 ),
hydrocarbons (gasoline vapor, methane, etc.),
compounds of heavy metals (lead, mercury, cadmium, etc.),
carbon dioxide ( CO 2).
Naturally, there may be other harmful gaseous substances in the air due to the presence of a particular production facility nearby. Emissions into the atmosphere are divided into:
1 – steam-gas and aerosol;
2 – technological and ventilation;
3 – organized and unorganized;
4 – heated and cold.
According to the 1st classification, vapor-gas emissions are a mixture of gases that do not contain solid or liquid particles. Aerosol emissions are a mixture of gases carrying solid or liquid particles.
Depending on the harmfulness of the gas components and the aerosol particles they contain, it is necessary to clean either one component of the mixture or the mixture as a whole. In the latter case, either combined cleaning in one apparatus or a combination of sequential arrangement of apparatuses is required.
Technological emissions are formed as a result of technological processes and represent emissions during blowing, emissions from safety valves, from boiler pipes, vehicles, etc. As a rule, they are characterized by a high concentration of pollutants. Ventilation emissions are characterized by large volumes of gas-air mixture, but low concentrations of pollutants. At the same time, due to the large volumes of the gas-air mixture, the gross emissions of pollutants with them can be significant.
Organized emissions include emissions removed by pipes or flues, which makes it quite easy to use gas and dust collection units. Unorganized emissions include emissions from depressurized equipment, emissions from unequipped places for loading or unloading materials, from transport systems, etc.
Hot or cold emissions are distinguished by the temperature difference between the gas and the surrounding environment. With a temperature difference of up to 30°C, emissions can be considered cold.
The operation of any device that removes suspended particles is based on the use of one or more sedimentation mechanisms. The main ones that have the greatest application include: gravitational deposition, deposition under the influence of centrifugal forces, inertial deposition, entanglement (touch effect), diffusion deposition, electrodeposition. Modern methods include thermophoresis and exposure to an electromagnetic field. The influence of a particular mechanism on the deposition of particles is determined by a number of factors, and primarily their size.
Gravity settling occurs as a result of particles settling vertically under the influence of gravity. When falling, a dust particle experiences resistance from the environment, so the speed of falling or settling is determined by the condition of equality of gravity and hydraulic resistance. Therefore, particles of smaller diameter will have a lower settling rate and to clean the air from such particles, a longer residence time of the dust-laden flow in the dust-sedimentation chamber will be required.
Centrifugal dust deposition is observed during the curvilinear movement of a dust-laden flow, when, under the influence of developed centrifugal forces, dust particles are thrown onto the deposition surface. In devices based on the use of centrifugal forces, two fundamental design solutions can be used. In one case, the dust and gas flow rotates in a stationary body of a cylindrical or conical apparatus. And in the second case, the dust and gas flow moves in a rotating rotor. The first solution is carried out in cyclones, and the second - in rotary dust collectors.
Inertial deposition occurs when the mass of a dust particle cannot follow along with the gas along a flow line enveloping a substance that is dense compared to air; due to inertia, when the flow turns, it continues to move in a straight line. In this case, a dust particle collides with an obstacle and settles on it. Inertial settling of dust particles is effective for particles larger than 1 micron.
Diffusive deposition will occur when particles, which are generally small in size, are subject to Brownian motion
molecules. As a result, they have an increased likelihood of contact with the streamlined body. The efficiency of diffusion deposition is inversely proportional to particle size and gas flow velocity.
The deposition of dust particles under the influence of an electric current consists of charging the particles and then separating them from the air under the influence of an electric field. Electrical charging of dust particles can be carried out during the generation of an aerosol, due to the diffusion of free currents and during a short discharge. In the latter case, dust particles are charged with the same sign, which makes it possible to increase the efficiency of their subsequent removal from the air flow.
Thermophoresis is the repulsion of particles by a heated body caused by the movement of air as a result of the occurrence of free convection. During thermophoresis, the concentration of particles in areas of high and low temperatures becomes different, which leads to thermal diffusion of particles towards lower temperatures. In practice, this can be observed in the form of dust deposited on the external walls against central heating appliances.
The deposition of suspended particles upon contact of a gas flow with a liquid can occur on drops, bubbles and on the surface of the liquid.
The capture of suspended particles by droplets is based on kinematic coagulation resulting from the difference in the velocities of particles and droplets.
This may happen:
When the aerosol moves at low speed and the liquid droplets fall under the influence of gravity;
When aerosol and droplets move in the same or opposite directions at different speeds.
When polluted air bubbles move through a layer of liquid (bubbling), a pulsation of gases occurs inside the bubbles. Suspended particles stick to the surface of the water surrounding the gas bubble.
When solid particles are deposited on the surface of a liquid, in the case when a gas flow moves along the liquid surface, the particles are deposited in the water in the volume of a thin film, i.e. surface water pollution occurs.
Gas filtration through porous materials involves passing the aerosol through filter baffles, which allow air to pass through but trap aerosol particles. The filtration process in the most common filters can be conventionally accepted as the process of flow around a cylinder located across the flow. Dust particles are retained on the surface of the fibers by molecular interaction forces. Filtration of a dusty flow through a porous material is much more complicated, since it involves not only the process of adhesion to the material as a result of flow, but also due to collision with fibers or threads. It must be taken into account that there are usually several rows of fibers along the path of the dusty flow, which increases the cleaning efficiency.
When extracting gaseous impurities, absorption, adsorption, catalysis and thermal oxidation methods are used.
Absorption purification is based on the ability of liquids to dissolve gases or chemically interact with them. During absorption, a substance transitions from the gas phase to the liquid phase. The substance in which the absorbed gas components are dissolved is called an absorbent. The remainder of the gas stream that is not absorbed into the liquid is usually called inert gas. During physical absorption, physical dissolution of the absorbed component in the solvent (absorbent) occurs. In this case, no chemical reactions occur. This process occurs when the partial pressure of the absorbed component in the gas is greater than the equilibrium partial pressure above the surface of the solution.
During chemical absorption (chemisorption), the absorbed component enters into a chemical reaction with the absorbent (liquid), forming new chemical compounds in the liquid phase. Chemisorption processes provide more complete extraction of components from gas mixtures. The amount of gases that can be dissolved in a liquid depends on the properties of the gas and liquid, the temperature and the partial pressure of the gas above the liquid.
The absorption process refers to the absorption of a gas component by a solid substance. The phenomenon of adsorption is due to the presence of attractive forces between the molecules of the adsorbent (solid) and the absorbed gas at the interface between the contacting phases. The process of transfer of molecules from gas to the surface layer of the adsorbent occurs if the attractive forces of the adsorbent exceed the attractive forces from the carrier gas. The molecules of the adsorbed substance, moving to the surface of the adsorbent, reduce its energy, resulting in the release of heat.
During physical adsorption, gas molecules do not enter into chemical interaction with adsorbent molecules. With increasing temperature, the amount of physically adsorbed substance decreases, and an increase in pressure leads to an increase in the amount of adsorption. The advantage of physical adsorption is the easy reversibility of the process.
Chemical adsorption is based on the chemical interaction between the adsorbent and the adsorbed substance. The forces acting in this case are much greater than during physical adsorption, and more heat is released. Gas molecules, having entered into chemical interaction with adsorbent molecules, are firmly held on the surface and in the pores of the adsorbent. It is characteristic that at low temperatures the rate of chemical adsorption is low, but it increases with increasing temperature.
Catalytic gas purification serves to convert impurities into harmless compounds. The process takes place on the surface of solid bodies - catalysts. The selection of catalysts is mainly decided empirically.
The catalysis process is greatly influenced by temperature. At relatively low temperatures, when the reaction rate is low compared to the rate of gas diffusion and the purification process is relatively slow. As the temperature rises, the rate of the chemical reaction increases, thereby increasing the rate of diffusion of gases. However, the diffusion rate increases more slowly and a moment may come when the gas purification process will be determined only by the rate of supply of reactants, and the use of the inner surface of the catalyst for this, as at the initial stage of the process, is close to zero. In this case, catalysis moves into the region of external diffusion. In this case, the small pores of the catalyst no longer play any role, but the role of the outer surface increases.
The most important characteristic of catalysts is the “ignition” temperature - the minimum temperature at which the catalyst begins to exhibit its properties.
Thermal oxidation of emission components is called oxidation at temperatures up to 1000°C. Oxidation is applied both to gases and to flammable components of the dispersed phase of aerosols. This method is used to extract resins, oils, volatile solvents and other components from gas streams. Of decisive importance in organizing the process is the preparation of gases for the reaction, i.e. heating the mixture to the required temperature and ensuring mixing of flammable gases with the oxidizer.
|
Sources of air pollution |
Treatment plants |
Note |
|
Boiler house running on liquid fuel |
Cyclone or cyclone battery Bag filters |
Calculation clause 4.6 Calculation clause 4.7 |
|
Boiler house operating on gaseous fuel |
Standalone offers |
Description of the method |
|
Solid fuel boiler room |
Cyclone battery Bag filters |
Calculation clause 4.6 Calculation clause 4.7 |
|
Painting and drying chamber |
Adsorber |
Calculation clause 4.8 |
|
Welding shop: welding production |
Venturi scrubber (KMP gas scrubber) |
Calculation clause 4.3 |
|
Mechanical shop: machine equipment |
Dust settling chamber Cyclone CN |
Calculation clause 4.2 |
|
Woodworking shop |
Dust settling chamber Cyclone Giprodrevprom |
Calculation clause 4.2 Calculation clause 4.6 |
|
Electroplating workshop |
Mesh mist eliminator |
Calculation clause 4.4 |
Air is a natural mixture of gases
When most of us hear the word “air,” a perhaps somewhat naive comparison involuntarily comes to mind: air is what we breathe. Indeed, the etymological dictionary of the Russian language indicates that the word “air” is borrowed from the Church Slavonic language: “to sigh.” From a biological point of view, air is therefore a medium for supporting life through oxygen. The air might not have contained oxygen - life would still have developed in anaerobic forms. But the complete absence of air apparently excludes the possibility of the existence of any organisms.
For physicists, air is primarily the earth’s atmosphere and the gas shell surrounding the earth.
But what is the air itself from a chemical point of view?
It took scientists a lot of effort, labor and patience to uncover this mystery of nature, that air is not an independent substance, as was believed more than 200 years ago, but is a complex mixture of gases. The scientist and artist Leonardo da Vinci (15th century) was the first to speak out about the complex composition of air.
About 4 billion years ago, the Earth's atmosphere consisted mainly of carbon dioxide. Gradually it dissolved in water and reacted with rocks, forming carbonates and bicarbonates of calcium and magnesium. With the advent of green plants, this process began to proceed much faster. By the time humans appeared, carbon dioxide, so necessary for plants, had already become scarce. Its concentration in the air before the start of the industrial revolution was only 0.029%. Over the course of 1.5 billion years, the oxygen content gradually increased.
Chemical composition of air
|
Components |
||
|
By volume |
By weight |
|
|
Nitrogen ( N 2) |
78,09 |
75,50 |
|
Oxygen (O 2) |
20,95 |
23,10 |
|
Noble gases (He, Ne, Ar, Kr, Xe, Rn, mainly argon) |
0,94 |
|
|
Carbon monoxide (IV) – carbon dioxide |
0,03 |
0,046 |
The quantitative composition of air was first established by the French scientist Antoine Laurent Lavoisier. Based on the results of his famous 12-day experiment, he concluded that all air as a whole consists of oxygen, suitable for respiration and combustion, and nitrogen, a non-living gas, in proportions of 1/5 and 4/5 of the volume, respectively. He heated metallic mercury in a retort on a brazier for 12 days. The end of the retort was brought under a bell placed in a vessel with mercury. As a result, the mercury level in the bell rose by about 1/5. An orange substance, mercury oxide, formed on the surface of the mercury in the retort. The gas remaining under the bell was unsuitable for breathing. The scientist suggested renaming “life air” to “oxygen”, since when burned in oxygen, most substances turn into acids, and “suffocating air” into “nitrogen”, because it does not support life, it harms life.
Lavoisier's experiment
The qualitative composition of air can be proven by the following experimentThe main component of air for us is oxygen; it is 21% by volume in the air. Oxygen is diluted with a large amount of nitrogen - 78% of the air volume and a relatively small volume of noble inert gases - about 1%. Air also contains variable components - carbon monoxide (IV) or carbon dioxide and water vapor, the amount of which depends on various reasons. These substances enter the atmosphere naturally. When volcanoes erupt, sulfur dioxide, hydrogen sulfide and elemental sulfur enter the atmosphere. Dust storms contribute to the appearance of dust in the air. Nitrogen oxides also enter the atmosphere during lightning electrical discharges, during which nitrogen and oxygen in the air react with each other, or as a result of the activity of soil bacteria that can release nitrogen oxides from nitrates; Forest fires and peatland burning also contribute to this. The processes of destruction of organic substances are accompanied by the formation of various gaseous sulfur compounds. The water in the air determines its humidity. Other substances have a negative role: they pollute the atmosphere. For example, there is a lot of carbon dioxide in the air of cities devoid of greenery, and water vapor above the surface of oceans and seas. The air contains small amounts of sulfur (IV) oxide or sulfur dioxide, ammonia, methane, nitric oxide (I) or nitrous oxide, and hydrogen. The air near industrial enterprises, gas and oil fields or volcanoes is especially saturated with them. There is another gas in the upper atmosphere - ozone. A variety of dust also flies in the air, which we can easily notice when looking from the side at a thin beam of light falling from behind a curtain into a darkened room.
Permanent components of air gases:
· Oxygen
· Nitrogen
· Noble gases
Variable components of air gases:
· Carbon monoxide (IV)
· Ozone
· Other
Conclusion.
1. Air is a natural mixture of gaseous substances, in which each substance has and retains its physical and chemical properties, so air can be separated.
2. Air is a colorless gaseous solution, density - 1.293 g/l, at temperatures -190 0 C it turns into a liquid state. Liquid air is a bluish liquid.
3. Living organisms are closely related to air substances, which have a certain effect on them. And at the same time, living organisms influence it because they perform certain functions: redox - they oxidize, for example, carbohydrates to carbon dioxide and reduce it to carbohydrates; gas - absorb and release gases.
Thus, living organisms created in the past and maintain the atmosphere of our planet for millions of years.
Air pollution - introduction of new uncharacteristic physical, chemical and biological substances into the atmospheric air or a change in the natural average long-term concentration of these substances in it.
The process of photosynthesis removes carbon dioxide from the atmosphere and returns it through the processes of respiration and decay. The balance established during the evolution of the planet between these two gases began to be disturbed, especially in the second half of the 20th century, when human influence on nature began to increase. For now, nature copes with disturbances in this balance thanks to ocean water and its algae. But will nature have enough strength for long?
Scheme. Air pollution
Main air pollutants in Russia
The number of cars is constantly growing, especially in large cities, and accordingly, the emission of harmful substances into the air is growing. Cars are responsible for 60% of harmful emissions in the city!
Russian thermal power plants emit up to 30% of pollutants into the atmosphere, and another 30% is the contribution of industry (ferrous and non-ferrous metallurgy, oil production and oil refining, chemical industry and production of building materials). The level of air pollution from natural sources is background ( 31–41%
), it changes little over time ( 59–69%
). Currently, the problem of anthropogenic atmospheric pollution has become global. What pollutants that are dangerous to all living things enter the atmosphere? These are cadmium, lead, mercury, arsenic, copper, soot, mercaptans, phenol, chlorine, sulfuric and nitric acids and other substances. We will study some of these substances in the future, find out their physical and chemical properties and talk about the destructive power they contain for our health.
The scale of environmental pollution of the planet, Russia
In which countries of the world is the air most polluted by vehicle exhaust fumes?
The greatest danger of air pollution from exhaust gases threatens countries with large vehicle fleets. For example, in the USA, motor vehicles account for approximately 1/2 of all harmful emissions into the atmosphere (up to 50 million tons annually). The car fleet of Western Europe annually emits up to 70 million tons of harmful substances into the air, and in Germany, for example, 30 million cars produce 70% of the total volume of harmful emissions. In Russia, the situation is aggravated by the fact that vehicles in use comply with environmental standards by only 14.5%.
It pollutes the atmosphere and air transport with plumes of exhaust from many thousands of aircraft. According to expert estimates, as a result of the activities of the global vehicle fleet (which is about 500 million engines), 4.5 billion tons of carbon dioxide alone are released into the atmosphere annually.
Why are these pollutants dangerous? Heavy metals - lead, cadmium, mercury - have a harmful effect on the human nervous system, carbon monoxide - on the composition of the blood; Sulfur dioxide, interacting with water from rain and snow, turns into acid and causes acid rain. What is the scale of this pollution? The main regions where acid rain occurs are the USA, Western Europe, and Russia. Recently, these include the industrial regions of Japan, China, Brazil, and India. The spread of acid precipitation is associated with the concept of transboundary nature - the distance between the areas of its formation and the areas of fallout can be hundreds and even thousands of kilometers. For example, the main “culprit” of acid rain in southern Scandinavia is the industrial areas of Great Britain, Belgium, the Netherlands and Germany. In the Canadian provinces of Ontario and Quebec, acid rain is transferred from neighboring areas of the United States. These precipitations are transported to Russian territory from Europe by westerly winds.
An unfavorable environmental situation has developed in the northeast of China, in the Pacific zone of Japan, in the cities of Mexico City, Sao Paulo, and Buenos Aires. In Russia in 1993, in 231 cities with a total population of 64 million people, the content of harmful substances in the air exceeded the norm. In 86 cities, 40 million people live in conditions where pollution exceeds standards by 10 times. Among these cities are Bryansk, Cherepovets, Saratov, Ufa, Chelyabinsk, Omsk, Novosibirsk, Kemerovo, Novokuznetsk, Norilsk, Rostov. The Ural region ranks first in Russia in terms of the amount of harmful emissions. Thus, in the Sverdlovsk region, the state of the atmosphere does not meet the standards in 20 territories, where 60% of the population lives. In the city of Karabash, Chelyabinsk region, a copper smelter annually emits 9 tons of harmful compounds into the atmosphere per inhabitant. The incidence of cancer here is 338 cases per 10 thousand inhabitants.
An alarming situation has also developed in the Volga region, in the south of Western Siberia, and in Central Russia. In Ulyanovsk, more people suffer from upper respiratory tract diseases than the Russian average. The incidence of lung cancer has increased 20-fold since 1970, and the city has one of the highest child mortality rates in Russia.
In the city of Dzerzhinsk, a large number of chemical enterprises are concentrated in a limited area. Over the past 8 years, there have been 60 releases of highly toxic substances into the atmosphere, leading to emergency situations, in some cases resulting in death. In the Volga region, up to 300 thousand tons of soot, ash, soot, and carbon oxides fall on city residents every year. Moscow ranks 15th among Russian cities in terms of total air pollution levels.
It is known that a person can live without food for more than one month, without water - only a few days, but without air - only a couple of minutes. Our body needs it! Therefore, the question of how to protect air from pollution should occupy a high priority among the problems of scientists, politicians, statesmen and officials of all countries. To avoid killing ourselves, humanity must take urgent measures to prevent this pollution. Citizens of any country are also obliged to take care of cleanliness. It just seems that practically nothing depends on us. There is hope that through joint efforts we can all protect the air from pollution, animals from extinction, and forests from deforestation.
Earth's atmosphere
Earth is the only planet known to modern science on which life exists, which was made possible thanks to the atmosphere. It ensures our existence. The atmosphere is, first of all, air, which must be suitable for breathing by people and animals, and not contain harmful impurities and substances. How to protect air from pollution? This is a very important issue that will have to be resolved in the near future.
Human activity
In recent centuries, we have often behaved extremely unreasonably. Mineral resources are wasted in vain. Forests are being cut down. The rivers are drying up. As a result, the natural balance is disrupted and the planet gradually becomes uninhabitable. The same thing happens with air. It is constantly polluted by all sorts of things entering the atmosphere. Chemical compounds contained in aerosols and antifreezes are destroying the Earth, threatening global warming and related disasters. How to protect air from pollution so that life on the planet continues?
The main reasons for the current problem
- Gaseous waste from factories and factories, released into the atmosphere in countless quantities. Previously, this happened completely uncontrollably. And on the basis of waste from enterprises that polluted the environment, it was possible to organize entire plants for their processing (as they do now, for example, in Japan).
- Cars. Burnt gasoline and diesel fuel form which escape into the atmosphere, seriously polluting it. And if you take into account that in some countries there are two or three cars for every average family, you can imagine the global nature of the problem under consideration.
- Combustion of coal and oil in thermal power plants. Electricity, of course, is extremely necessary for human life, but extracting it in this way is real barbarity. When burning fuel, a lot of harmful emissions are generated, which heavily pollute the air. All impurities rise into the air with smoke, are concentrated in clouds, and spill onto the soil in the form of trees, which are intended to purify oxygen, and suffer greatly from this.
How to protect air from pollution?
Measures to prevent the current catastrophic situation have long been developed by scientists. All that remains is to follow the prescribed rules. Humanity has already received serious warnings from nature itself. Especially in recent years, the world around us is literally shouting to people that the consumer attitude towards the planet must be changed, otherwise - the death of all living things. What do we have to do? How to protect the air from pollution (pictures of our amazing nature are presented below)?
According to environmental experts, such measures will contribute to a significant improvement in the current situation.
The materials presented in the article can be used in a lesson on the topic “How to protect air from pollution” (grade 3).
LECTURE 14.
MEASURES AND MEANS FOR PROTECTING ATMOSPHERIC AIR FROM POLLUTION
Lecture outline:
Basic ways to protect the atmosphere from industrial pollution.
Purification of process and ventilation emissions. Purification of exhaust gases from aerosols.
1. Basic ways to protect the atmosphere from industrial pollution.
Environmental protection is a complex problem that requires the efforts of scientists and engineers of many specialties. The most active form of environmental protection is:
Creation of waste-free and low-waste technologies;
Improving technological processes and developing new equipment with lower emissions of impurities and waste into the environment;
Environmental assessment of all types of production and industrial products;
Replacing toxic waste with non-toxic waste;
Replacement of non-recyclable waste with recycled ones;
Widespread use of additional methods and means of environmental protection.
The following are used as additional environmental protection measures:
devices and systems for purifying gas emissions from impurities;
relocation of industrial enterprises from large cities to sparsely populated areas with unsuitable and unsuitable lands for agriculture;
optimal location of industrial enterprises, taking into account the topography of the area and the wind rose;
establishment of sanitary protection zones around industrial enterprises;
rational planning of urban development providing optimal conditions for people and plants;
organizing traffic in order to reduce the release of toxic substances in residential areas;
organization of environmental quality control.
Sites for the construction of industrial enterprises and residential areas must be selected taking into account the aeroclimatic characteristics and terrain.
The industrial facility must be located on a flat, elevated place, well blown by winds.
The residential building site should not be higher than the enterprise site, otherwise the advantage of high pipes for dispersing industrial emissions is practically eliminated.
The relative location of enterprises and settlements is determined by the average wind rose of the warm period of the year. Industrial facilities, which are sources of emissions of harmful substances into the atmosphere, are located outside populated areas and downwind of residential areas.
The requirements of the “Sanitary Standards for the Design of Industrial Enterprises SN 245 71” stipulate that objects that are sources of release of harmful and unpleasantly smelling substances should be separated from residential buildings by sanitary protection zones. The dimensions of these zones are set depending on:
enterprise capacity;
conditions for the implementation of the technological process;
the nature and quantity of harmful and unpleasant-smelling substances released into the environment.
Five sizes of sanitary protection zones have been established: for class I enterprises - 1000 m, class II - 500 m, class III - 300 m, class IV - 100 m, class V - 50 m.
Machine-building enterprises, in terms of the degree of environmental impact, mainly belong to classes IV and V.
The sanitary protection zone can be increased, but not more than three times, by decision of the Main Sanitary and Epidemiological Directorate of the Ministry of Health of Russia and the State Construction Committee of Russia in the presence of unfavorable aerological conditions for the dispersion of industrial emissions in the atmosphere or in the absence or insufficient efficiency of treatment facilities.
The dimensions of the sanitary protection zone can be reduced by changing technology, improving the technological process and introducing highly efficient and reliable treatment devices.
The sanitary protection zone is prohibited from being used to expand an industrial site.
It is allowed to place objects of a lower hazard class than the main production, fire station, garages, warehouses, administrative buildings, research laboratories, parking lots, etc.
The sanitary protection zone must be landscaped and landscaped with gas-resistant trees and shrubs. On the side of the residential area, the width of green spaces should be at least 50 m, and with a zone width of up to 100 m - 20 m.
2. Purification of process and ventilation emissions. Purification of exhaust gases from aerosols.
The process of purifying gases from solid and droplet impurities in various devices is characterized by several parameters, including the overall purification efficiency:
If cleaning is carried out in a system of series-connected devices, then the cleaning efficiency is:
= 1 (1 1)(1 2)…(1 n).
E 
efficiency of fractional purification:
D 
To assess the efficiency of the process, the coefficient of particle breakthrough K through the filter is used:
Specific dust capacity of the dust collector:
The amount of dust that it retains during the period of continuous operation between two subsequent regenerations. Specific dust holding capacity is used in calculating the duration of filter operation between regenerations.
The efficiency of dust collection depends on the physical and chemical properties of dust and mists:
dispersed composition;
density;
adhesion properties;
wettability;
electrical charge of particles;
resistivity of particle layers.
To correctly select a dust collecting apparatus, you first need information about the dispersed composition of dust and mists.
Based on dust dispersion, they are classified into five groups:
I – very coarse dust, d 50 > 140 µm.
II - coarse dust, d 50 = 40-140 microns.
III - medium-sized dust, d 50 = 10-40 microns.
IV - fine dust, d 50 = 1-10 microns.
V – very fine dust, d 50< 1 мкм.
Adhesive properties - the tendency of dust particles to stick together. The finer the dust, the higher its stickiness.
The wettability of particles by liquid (water) affects the operation of wet dust collectors.
Gas purification in dry dust collectors.
Dry mechanical dust collectors include devices that use various sedimentation mechanisms: gravitational, inertial and centrifugal.
Devices using these principles are easy to manufacture and operate, and they are widely used in industry. However, the capture efficiency in them is not always sufficient, and therefore they often serve as gas pre-purification devices.
Cyclones. Cyclone devices are the most common in industry.
Advantages:
a) the absence of moving parts in the device;
b) reliability of operation at temperatures up to 500°C;
c) the possibility of trapping abrasive particles while protecting internal parts with special coatings;
d) dry dust collection;
e) successful operation at high gas pressures;
f) ease of manufacture;
h) maintaining high cleaning efficiency with increasing gas dust content.
Flaws:
a) high hydraulic resistance;
b) poor capture of particles smaller than 5 microns;
c) inability to use for purifying gases from sticky contaminants.
Vortex dust collectors. The main difference between vortex dust collectors and cyclones is the presence of an auxiliary swirling gas flow. A distinctive feature of the VPU is the efficiency of gas purification from the finest fractions (< 3-5 мкм).
Gas purification in filters.
Filters are widely used for fine purification of gas emissions from aerosols. The operation of all types of porous filters is based on the process of gas filtration through a porous partition, during which solid particles are retained and the gas passes completely through it. Filter partitions are very diverse in their structure and are conventionally divided into the following types:
flexible porous partitions - fabric materials made from natural, synthetic or mineral fibers; non-woven fibrous materials (felts, glued and needle-punched materials, paper, cardboard, fibrous sheets); cellular sheets (sponge rubber, polyurethane foam, membrane filters);
semi-rigid porous partitions - a layer of fibers, shavings, knitted meshes located on supporting devices or sandwiched between them;
hard porous partitions - granular materials (porous ceramics or plastics, sintered or pressed metal powders, porous glasses, carbon-graphite materials); metal mesh and perforated sheets.
Depending on the purpose and value of the input and output concentrations, filters are divided:
Fine filters are designed to capture with very high efficiency (>99) submicron particles from industrial gases (with C<1 мг/м 3) и скоростью фильтрования <100 м/с. Применяются для улавливания токсичных частиц. Эти фильтры не подвергаются регенерации.
Air filters are used in supply ventilation and air condensation systems. Work at C<50 мг/м 3 , при V=2,5-3,0 м/с; они могут быть регенерируемыми или нерегенерируемыми.
Industrial filters (fabric, granular, coarse fiber) are used to purify industrial gases with concentrations up to 60 g/m 3 . Filters are regenerated.
Fabric filters. These filters are the most common. The possibilities of their use are expanding due to the creation of new temperature-resistant fabrics that are resistant to aggressive gases. Bag filters are the most common.
Fine filters used in nuclear energy, radio electronics, precision instrument making, industrial microbiology and other industries. Filters make it possible to purify large volumes of gases from solid particles of all sizes, including submicron ones. They are widely used to purify radioactive aerosols. For 99% purification (for particles 0.05-0.5 microns), materials are used in the form of thin sheets or bulk layers of thin or ultra-fine fibers (d< 2 мкм). Скорость фильтрации 0,01-0,15 м/с.
In Russia, filter materials of the FP type (Petryanov filters) made of polymer threads are widely used. Perchlorovinyl (PVC) and cellulose diacetate (CPA) are used as polymers.
Two-stage or combined filters. In one housing there are coarse filters made of a layer of lavsan threads d = 100 microns and fine filters made of FP material.
Grain filters. There are attachment and rigid granular filters.
Packed (bulk) filters. In bulk filters, sand, pebbles, slag, crushed rocks, sawdust, coke, rubber crumbs, plastics, and graphite are used as a nozzle. The filters have a nozzle with a grain size of 0.2-2 mm.
Grainy hard filters. In these filters, the grains are firmly bonded to each other by sintering, pressing or gluing and form a strong, stationary system. These include porous ceramics, porous metals, porous plastics. These filters are used to purify compressed gases.
Gas purification in wet dust collectors.
Wet filters have a number of advantages and disadvantages over other devices.
Advantages:
a) low cost and higher efficiency of trapping suspended particles;
b) the possibility of using for gas purification from particles up to 0.1 microns;
c) the ability to purify gases at high temperatures and high humidity, as well as when there is a risk of fire and explosions of purified gases and captured dust;
d) the ability to capture vapor and gaseous components along with dust.
Flaws:
a) release of captured dust in the form of sludge, which is associated with the need for wastewater treatment, which increases the cost of the process;
b) the possibility of entrainment of liquid droplets and their deposition with dust in flues and smoke exhausters;
c) in the case of cleaning aggressive gases, it is necessary to protect equipment and communications with anti-corrosion materials.
In wet dust collectors, water is most often used as a spray liquid. Depending on the contact surface or method of action, they are divided into 7 types:
hollow gas scrubbers;
packed scrubbers;
disc (bubbling, foam) scrubbers;
scrubbers with a moving nozzle;
shock-inertial gas scrubbers;
centrifugal scrubbers;
mechanical gas scrubbers.
Hollow gas scrubbers. They are the most common. Based on the direction of movement of gas and liquid, they are divided into counter-flow, direct-flow and with transverse liquid supply. When working without drop eliminators V=0.6-l.2 m/s; from drop eliminators - 5-8 m/s. Provides high cleaning performance for dust particles with a size of 10 microns and is ineffective at d h<5 мкм.
Attachment gas scrubbers. They are used to capture well-wetted dust, but at a low concentration. Due to frequent clogging, such washers are rarely used. Liquid consumption is 0.15-0.5 l/m 3 of gas, the efficiency at trapping particles >2 microns exceeds 90%.
Gas scrubbers with movable nozzle. They are widely used in dust collection. Balls made of polymer materials, glass or porous rubber are used as nozzles. The density of the nozzle balls should not exceed the density of the liquid.
To ensure a high degree of dust collection, the following process parameters are recommended: W=5-6 m/s; specific irrigation - 0.5-0.7 l/m 3; free section of the plate 0.4 m 2 / m 2 with a slot width of 4-6 mm. Ball size 20-40 mm.
Conical scrubbers with a movable ball nozzle. Two types - nozzle and ejection. The devices use polyethylene balls 35-40 mm with a bulk density of 110-120 kg/m 3. The height of the layer of balls is 650 mm, W g.in. = 6-10 m/s, W g.out. = 1-2 m/s, H K = 1 m, = 10-60°, Q = from 3000 to 40000 m 3 /h.
Disc gas scrubbers (bubbling, foam). The most common foam machines are those with sink plates or overflow plates. Overflow plates have holes 3-8 mm and a free cross-section of 0.15-0.25 m 2 / m 2.
Failure plates can be perforated, slotted, tubular, or grate. Hole plates have holes 4-8 mm. The width of the slots in other designs is 4-5 mm. Free section 0.2-0.3 m2/m2. Dust is captured by a foam layer, which is formed by the interaction of gas and liquid. Modern bubbling-foam devices provide an efficiency of gas purification from fine dust of 0.95-0.96 at a specific water consumption of 0.4-0.5 l/m 3 .
Gas scrubbers of shock-inertial action. In these devices, the contact of gases with liquid is achieved due to the impact of the gas flow on the surface of the liquid. As a result of this interaction, droplets 300-400 µm are formed. The gas speed is 35-55 m/s, the specific liquid flow is 0.13 l/m 3.
Centrifugal gas scrubbers. Based on their design, they are divided into 2 types:
devices in which the gas flow is swirled using a central blade swirl device;
devices with lateral tangential gas supply.
Most domestic centrifugal scrubbers have a tangential gas supply and film irrigation. Such devices are used to clean all types of non-cementing dust.
To clean flue gases from ash, a centrifugal scrubber TsS-VTI is used. The specific water consumption is 0.09-0.18 l/m3.
High-speed gas scrubbers (Venturi scrubbers) . The main part of the apparatus is a spray pipe, which provides intensive crushing of the irrigating liquid by a gas flow moving at a speed of 40-150 m/s. There is a drip eliminator.
The cleaning efficiency is 0.96-0.98 for particles with an average size of 1-2 microns with an initial dust concentration of up to 100 g/m3. Specific water consumption is 0.1-6.0 l/m3. Gas capacity up to 85,000 m 3 /h. Venturi scrubbers are widely used in gas removal systems. The efficiency of air purification from fog with an average particle size of 0.3 microns reaches 0.999, which is quite comparable with high-efficiency filters.
Mist eliminators. To purify the air from mists of acids, alkalis, oils and other liquids, fiber filters are used, the operating principle of which is based on the deposition of droplets on the surface of the pores, followed by the flow of liquid under the influence of gravity.
Fog eliminators are divided into low-speed (W f 0.15 m/s) and high-speed (W f = 2-2.5 m/s), where deposition occurs under the influence of inertial forces.
Fiber low-velocity mist eliminators provide high efficiency (up to 0.999) for gas purification from particles smaller than 3 microns and completely capture larger particles. Fibrous layers are formed by packing glass fiber with a diameter of 7 to 30 microns or polymer fibers (lavsan, polypropylene) with a diameter of 12 to 40 microns. The layer thickness is 5-15 mm. The hydraulic resistance of dry filter elements is 200-1000 Pa.
High-speed mist eliminators have smaller overall dimensions and provide a cleaning efficiency of 0.9-0.98 at P = 1500-2000 Pa from fog with particles less than 3 microns. Felts made of polypropylene fibers are used as filter packing, which work successfully in the environment of dilute and concentrated acids (H 2 SO 4, HCl, HF, H 3 PO 4, HNO 3) and strong alkalis.
To clean the aspiration air of chrome plating baths, containing fog and splashes of chromic and sulfuric acids, fiber filters of the FVG-T type are used. The housing contains a cassette with filter material - needle-punched felt (TU 17-14-77-79), consisting of fibers 70 microns, layer thickness 4-5 mm. Hydraulic resistance 0.15-0.5 kPa, Q = 3500-80000 m 3 /h, cleaning efficiency 0.96-0.99, t90°C.
Gas purification in electric precipitators. In electric precipitators, gases are purified from dust under the influence of electrical forces.
The most common electrostatic precipitators are those with plate and tubular electrodes. In plate electrostatic precipitators, corona wires are stretched between the precipitation plate electrodes. In tubular electrostatic precipitators, the precipitation electrodes are cylinders (tubes), inside of which corona electrodes are located along the axis.
Electric precipitators clean large volumes of gases from dust with particles ranging in size from 0.01 to 100 microns at t=450 °C, P = 150 Pa. Specific electricity costs are 0.36-1.8 MJ per 1000 m 3 of gas. Efficiency 0.999.
Purification of process and ventilation emissions from gas and vapor pollutants
The processes of purification and neutralization of technological and ventilation emissions from engineering enterprises from gas and vapor impurities are characterized by the fact that, firstly, the gases emitted into the atmosphere are very diverse in chemical composition; secondly, they sometimes have a high temperature and contain a large amount of dust, which significantly complicates the gas purification process and requires preliminary preparation of the exhaust gases; thirdly, the concentration of gaseous and vaporous impurities, often in ventilation and less often in process emissions, is usually variable and low.
Gas cleaning installations created in industry make it possible to neutralize process and ventilation emissions without or with subsequent disposal of captured impurities. Devices that isolate the product in concentrated form and then use it in the production cycle are the most promising. The production of such installations is the most important stage in the development of low-waste and waste-free technology.
Methods for purifying industrial emissions from gaseous pollutants are divided into five groups based on the nature of the physical and chemical processes:
physical absorption;
chemisorption;
absorption of gaseous impurities by solid sorbents (adsorption);
thermal neutralization of waste gases;
catalytic purification of exhaust gases.
Absorption method. In gas emissions cleaning technology, the absorption process is often called the scrubber process. Purification of gas emissions by the absorption method involves separating a gas-air mixture into its component parts by absorbing one or more gas components (absorbates) of this mixture with liquid absorbers (absorbents) to form solutions.
The driving force here is the concentration gradient at the gas-liquid interface. The component of the gas-air mixture (absorbate) dissolved in the liquid penetrates into the internal layers of the absorbent due to diffusion. The purification process proceeds the faster, the larger the phase interface, flow turbulence and diffusion coefficients. Therefore, in the process of designing absorbers, special attention should be paid to the organization of contact of the gas flow with the liquid solvent and the selection of the absorbing liquid (absorbent).
The decisive condition when choosing an absorbent is the solubility of the extracted component in it and its dependence on temperature and pressure.
Water is used as an absorbent for physical absorption (to absorb gases such as NH 3, HC1, HF, etc.). In some special cases, high-boiling organic solvents are used as an absorbent to capture aromatic hydrocarbons that are poorly soluble in water.
The organization of contact of the gas flow with the absorbent is carried out either by passing gas through a packed column, or by spraying liquid, or by bubbling gas through the absorbent layer.
Depending on the implemented method of gas-liquid contact, there are:
a) packed columns;
b) hollow spray columns;
c) Venturi scrubbers;
d) bubbling disc columns.
As a nozzle, geometric bodies of various shapes are used, each of which is characterized by its own specific surface area and resistance to the movement of gas flow (Raschig rings, Berle saddles, Pall rings, Intalox saddles). Material: ceramics, porcelain, plastics, metal.
Method chemisorption. It is based on the absorption of gases and vapors by liquid absorbers with the formation of low-volatile or slightly soluble chemical compounds. The absorption capacity of a chemisorbent is almost independent of pressure, so chemisorption is more beneficial when the concentration of harmful impurities in the exhaust gases is low. Most of the reactions occurring in the process of chemisorption are exothermic and reversible, therefore, when the temperature of the solution increases, the resulting chemical compounds decompose with the release of the original elements. The desorption mechanism of the chemisorbent is based on this principle.
An example of chemisorption is the purification of a gas-air mixture from hydrogen sulfide and carbon dioxide using arsenic-alkaline, ethanolamine and other solutions.
Chemisorption is one of the common methods of purifying exhaust gases from nitrogen oxides. To purify gases from nitrogen oxides released from pickling baths, a Venturi scrubber with nozzle irrigation of gases with a lime solution is used. Gases from pickling baths containing nitrogen oxides, vapors of sulfuric, hydrochloric and hydrofluoric acids are sent to a scrubber, where they come into contact with a lime solution and are neutralized. The efficiency of purification from nitrogen oxides is 0.17-0.86 and from acid vapors - 0.95.
Copper-ammonia solutions are used to purify exhaust gases from carbon monoxide.
Method adsorption is based on the physical properties of some solids with a developed pore surface to selectively extract and concentrate individual components from a gas mixture on their surface.
Adsorption is divided into physical and chemisorption. In physical adsorption, gas molecules are adsorbed on the surface of a solid under the influence of intermolecular attractive forces. The advantage of physical adsorption is the reversibility of the process.
Chemisorption is based on the chemical interaction between the adsorbent and the adsorbed substance. The chemisorption process is usually irreversible.
Substances having a large surface area per unit mass are used as adsorbents or absorbers. Activated carbon, as well as simple and complex oxides (activated alumina, silica gel, activated alumina, synthetic zeolites or molecular sieves) are used as adsorbents. One of the main parameters when choosing an adsorbent is the adsorption capacity of the extracted component.
Structurally, devices for carrying out the adsorption process (adsorber) are made in the form of vertical, horizontal, or annular containers filled with a porous adsorbent through which the flow of the purified gas is filtered.
Adsorption is widely used in the purification of gas emissions from organic solvent vapors to remove toxic components (hydrogen sulfide) from gas streams emitted into the atmosphere, to remove radioactive gases during the operation of nuclear reactors, in particular radioactive iodine, and in other processes of purifying air from harmful impurities.
Thermal neutralization. The method is based on the ability of flammable toxic components (gases, vapors and strong-smelling substances) to oxidize to less toxic ones in the presence of free oxygen and high temperature of the gas mixture. This method is used in cases where emissions are large and pollutant concentrations exceed 300 ppm.
Methods for thermal neutralization of harmful impurities in many cases have advantages over absorption and adsorption:
a) absence of sludge management;
b) small dimensions of treatment plants;
