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Technical means and methods for protecting the atmosphere. Methods and means of protecting the atmosphere Basic methods of protecting the atmosphere from chemical impurities Atmospheric pollution and its quality control

In order to protect the atmosphere from pollution, the following environmental protection measures are used:

– greening of technological processes;

– purification of gas emissions from harmful impurities;

– dispersion of gaseous emissions in the atmosphere;

– compliance with the standards of permissible emissions of harmful substances;

– arrangement of sanitary protection zones, architectural and planning solutions, etc.

Greening of technological processes is primarily the creation of closed technological cycles, waste-free and low-waste technologies that exclude harmful pollutants from entering the atmosphere. In addition, it is necessary to pre-clean the fuel or replace it with more environmentally friendly types, the use of hydro-dedusting, gas recirculation, the transfer of various units to electricity, etc.

The most urgent task of our time is to reduce air pollution from exhaust gases of cars. Currently, there is an active search for an alternative, more "environmentally friendly" fuel than gasoline. The development of electric car engines continues, solar energy, alcohol, hydrogen, etc.

Purification of gas emissions from harmful impurities. The current level of technology does not allow for the complete prevention of the entry of harmful impurities into the atmosphere with gas emissions. Therefore, various methods of cleaning exhaust gases from aerosols (dust) and toxic gas and vapor impurities (NO, NO2, SO2, SO3, etc.) are widely used.

For the purification of emissions from aerosols, Various types devices depending on the degree of dustiness of the air, the size of solid particles and the required level of cleaning: dry dust collectors(cyclones, dust collectors), wet dust collectors(scrubbers, etc.), filters, electrofilters(catalytic, absorption, adsorption) and other methods for cleaning gases from toxic gas and vapor impurities.

Dispersion of gas impurities in the atmosphere - this is the reduction of their hazardous concentrations to the level of the corresponding MPC by dispersing dust and gas emissions using high chimneys. The higher the pipe, the greater its scattering effect. Unfortunately, this method makes it possible to reduce local pollution, but at the same time, regional pollution appears.

Arrangement of sanitary protection zones and architectural and planning measures.

Sanitary protection zone (SPZ) – this is a strip separating sources of industrial pollution from residential or public buildings to protect the population from the influence of harmful production factors. The width of these zones ranges from 50 to 1000 m, depending on the class of production, the degree of harmfulness and the amount of substances released into the atmosphere. At the same time, citizens whose dwelling is within the SPZ, protecting their constitutional right to a favorable environment, can demand either the termination of the environmentally hazardous activities of the enterprise, or relocation at the expense of the enterprise outside the SPZ.

Architectural and planning activities include the correct mutual placement of emission sources and populated areas, taking into account the direction of the winds, the choice of a flat, elevated place for building an industrial enterprise, well blown by the winds, etc.

Previous materials:

6.5. MEANS OF PROTECTION OF THE ATMOSPHERE.

The air of industrial premises is polluted by emissions from technological equipment or during technological processes without localization of waste substances. Ventilation air removed from the premises can cause air pollution in industrial sites and populated areas. In addition, air

is polluted by technological emissions from workshops, such as forging and pressing workshops, workshops for thermal and mechanical processing of metals, foundries and others, on the basis of which modern engineering develops. In the process of manufacturing machinery and equipment, welding, metal machining, processing of non-metallic materials, paint and varnish operations, etc. are widely used. Therefore, the atmosphere needs to be protected.

Means of protection of the atmosphere should limit the presence of harmful substances in the air of the human environment at a level not exceeding the MPC. This is achieved by localization of harmful substances in the place of their formation, removal from the room or equipment and dispersion in the atmosphere. If at the same time the concentration of harmful substances in the atmosphere exceeds the MPC, then the emissions are cleaned from harmful substances in the cleaning devices installed in the exhaust system. The most common are ventilation, technological and transport exhaust systems.

In practice, the following options for protecting atmospheric air are implemented:

removal of toxic substances from the premises by general ventilation;


ventilation, purification of polluted air in special devices and
its return to the production or household premises, if the air
after cleaning in the apparatus meets the regulatory requirements for
supply air,

localization of toxic substances in the zone of their formation local
ventilation, purification of polluted air in special devices,
release and dispersion in the atmosphere,

purification of technological gas emissions in special devices,
release and dispersion in the atmosphere; in some cases before release
exhaust gases are diluted with atmospheric air.

To comply with the MPC of harmful substances in the atmospheric air of populated areas, the maximum permissible emission (MAE) of harmful substances from exhaust ventilation systems, various technological and power plants is established.

In accordance with the requirements of GOST 17.2.02, for each projected and operating industrial enterprise, the MPE of harmful substances into the atmosphere is set, provided that emissions of harmful substances from this source in combination with other sources (taking into account the prospects for their development) do not create a surface concentration exceeding the MPC .

Devices for cleaning ventilation and technological emissions into the atmosphere are divided into:

dust collectors (dry, electric filters, wet filters);

mist eliminators (low and high speed);

devices for capturing vapors and gases (absorption,
chemisorption, adsorption and neutralizers);

multi-stage cleaning devices (dust and gas traps,
mist and particulate traps, multi-stage
dust collectors).

Electric cleaning (electrostatic precipitators) is one of the most advanced types of gas cleaning from dust and fog particles suspended in them. This process is based on the impact ionization of gas in the zone of the corona discharge, the transfer of the ion charge to impurity particles and the deposition of the latter on the precipitation corona electrodes. For this, electrofilters are used.


Scheme of the electrostatic precipitator.

1-corona electrode

2-collecting electrode

Aerosol particles entering the zone between the corona 1 and collecting 2 electrodes adsorb ions on their surface, acquiring an electric charge, and thereby receive an acceleration directed towards the electrode with a charge of the opposite sign. Considering that the mobility of negative ions in air and flue gases is higher than positive ones, electrostatic precipitators are usually made with a corona of negative polarity. The charging time of aerosol particles is short and is measured in fractions of a second. The movement of charged particles to the collecting electrode occurs under the action of aerodynamic forces and the force of interaction between the electric field and the charge of the particle.

The filter is a housing 1, divided by a porous partition (filter element) 2 into two bands. Contaminated gases enter the filter, which are cleaned when passing through the filter element. Particles of impurities settle on the inlet part of the porous partition and linger in the pores, forming layer 3 on the surface of the partition. For newly arriving particles, this layer becomes part of the filter partition, which increases the purification efficiency

filter and pressure drop across the filter element. Deposition of particles on the surface of the pores of the filter element occurs as a result of the combined action of the touch effect, as well as diffusion, inertial and gravitational.

Wet dust collectors include bubbling-foam dust collectors with failure and overflow grates.


Diagram of bubbling-foam dust collectors with failure (a) and (b)

overflow gratings.

3-lattice

In such devices, the gas for purification enters under the grate 3, passes through the holes in the grate and, bubbling through the layer of liquid and foam 2, is cleaned of dust by deposition of particles on the inner surface of the gas bubbles. The mode of operation of the devices depends on the speed of air supply under the grate. At a speed of up to 1 m/s, a bubbling mode of operation of the apparatus is observed. A further increase in the gas velocity in the body 1 of the apparatus up to 2...2.5 m/s is accompanied by the appearance of a foam layer above the liquid, which leads to an increase in the efficiency of gas purification and spray entrainment from the apparatus. Modern bubbling-foam devices provide the efficiency of gas purification from fine dust -0.95...0.96 at a specific water consumption of 0.4...0.5 l/m. The practice of operating these devices shows that they are very sensitive to the uneven supply of gas under the failed gratings. Uneven gas supply leads to local blow-off of the liquid film from the grate. In addition, the grates of the apparatus are prone to clogging.

To clean the air from mists of acids, alkalis, oils and other liquids, fibrous filters - mist eliminators are used. The principle of their operation is based on the deposition of drops on the surface of the pores, followed by the flow of liquid along the fibers to the lower part of the mist eliminator. Deposition of liquid droplets occurs under the action of Brownian diffusion or an inertial mechanism for separating pollutant particles from the gas phase on the filter elements, depending on the filtration rate W. The mist eliminators are divided into low-speed (W< 0,15 м/с), в которых преобладает механизм диффузного осаждения капель, и высокоскоростные (W=2...2,5 м/с), где осаждение происходит главным образом под воздействием инерционных сил.

Felts made of polypropylene fibers are used as filter packing in such mist eliminators, which successfully operate in dilute and concentrated acids and alkalis.

In cases where the diameter of the fog droplets is 0.6...0.7 µm or less, in order to achieve an acceptable cleaning efficiency, it is necessary to increase the filtration rate to 4.5...5 m/s, which leads to a noticeable spray entrainment from the output side of the filter element (spray usually occurs at speeds of 1.7 ... To trap liquid particles larger than 5 microns, spray traps from mesh packages are used, where liquid particles are captured due to touch effects and inertial forces. The filtration speed in the spray traps must not exceed 6 m/s.

Diagram of a high-speed fog eliminator.

1 - sprinkler

3-filter element

High-speed mist eliminator with a cylindrical filter element 3, which is a perforated drum with a blind cover. Coarse-fiber felt 2 with a thickness of 3...5 mm is installed in the drum. Around the drum on its outer side there is a spray trap 1, which is a set of perforated flat and corrugated layers of vinyl plastic tapes. The splash trap and the filter element are installed in the liquid layer at the bottom.


Diagram of the filter element of a low-velocity mist eliminator

3-cylinders

4 fiber filter element

5-bottom flange

6-pipe water seal

In the space between the cylinders 3, made of grids,
a fibrous filter element 4 is placed, which is attached with
flange 2 to the body of the mist eliminator 1. Liquid deposited on
filter element; flows down to the lower flange 5 and through the tube
water seal 6 and glass 7 is drained from the filter. fibrous
low speed mist eliminators provide high

the efficiency of gas purification (up to 0.999) from particles smaller than 3 microns and completely trap large particles. Fibrous layers are formed from fiberglass with a diameter of 7...40 microns. The layer thickness is 5...15 cm, the hydraulic resistance of dry filter elements is 200...1000 Pa.

High-speed mist eliminators are smaller and provide cleaning efficiency equal to 0.9...0.98 at Ap=1500...2000 Pa from mist with particles less than 3 microns.


BIBLIOGRAPHY.

Arshinov V. A., Alekseev G. A. Metal cutting and cutting
tool. Ed. 3rd, revised. and additional Textbook for engineering colleges. M.: Mashinostroenie, 1976.

Baranovsky Yu. V., Brakhman L. A., Brodsky Ts. Z. et al. Re
metal cutting presses. Directory. Ed. 3rd, revised and expanded. M.: Mashinostroenie, 1972.

Barsov AI Technology of tool production.
Textbook for engineering colleges. Ed. 4th, corrected and supplemented. M.: Mashinostroenie, 1975.

GOST 2848-75. Tool cones. Tolerances. Methods and
means of control.

GOST 5735-8IE. Machine reamers equipped with hard alloy inserts. Specifications.

Granovsky G. I., Granovsky V. G. Metal cutting: Textbook
nickname for machine building and instrumentation specialist. universities. M.: Higher. school,
1985.

Inozemtsev GG Design of metal-cutting tools: Proc. allowance for higher educational institutions in the specialty
"Technology of mechanical engineering, metal-cutting machines and tools". M.: Mashinostroenie, 1984.

Nefedov N. A., Osipov K. A. Collection of problems and examples on
metal cutting and cutting tool: Proc. allowance for
technical schools on the subject "Fundamentals of the doctrine of cutting metals and
cutting tool". 5th ed., revised. and additional Moscow: Mashino
building, 1990.

Fundamentals of mechanical engineering technology. Ed. B.C. Korsakov. Ed. 3rd, add. and reworked. Textbook for high schools. M.: Mashinostroenie, 1977.


Industry methodology for determining the economic efficiency of the use of new technology, inventions and rationalization proposals.

Sakharov G. P., Arbuzov O. B., Borovoy Yu. M.: Mashinostroenie, 1989.


Ed. 3rd revision. T. 1. Ed. A. G. Kosilova and R. K. Meshcheryakov. M.: Mashinostroenie, 1972.

Handbook of technologist-machine builder. In two volumes.
Ed. 3rd revision. T. 2. Ed. A. N. Malova. Moscow: Mashino
building, 1972.

Taratynov O. V., Zemskov G. G., Baranchukova I. M. and others.
Metal-cutting systems of machine-building industries:
Proc. manual for students of technical universities. M.: Higher.
school, 1988.

Taratynov O. V., Zemskov G. G., Taramykin Yu. P. et al.
Design and calculation of metal-cutting tools for
COMPUTER:. Proc. allowance for universities. M.: Higher. school, 1991.

Turchin A. M., Novitsky P. V., Levshina E. S. et al. Electric measurements of non-electric quantities. Ed. 5th, revised. and additional L.: Energy, 1975.

Khudobin L. V., Grechishnikov V. A. et al. Guide to diploma design in engineering technology, metal-cutting machines and tools: Proc. manual for universities in the specialty "Technology of mechanical engineering, metal-cutting machines and tools." M., Mashinostroenie, 1986.

Yudin E. Ya., Belov S. V., Balantsev S. K. and others. Labor protection
in mechanical engineering: Textbook for engineering universities.
M.: Mashinostroenie, 1983.

Guidelines to the practical lesson "Calculation
mechanical ventilation of industrial premises. / B.
S. Ivanov, M.: Rotaprint MASI (VTUZ-ZIL), 1993.

Guidelines for diploma design
"Regulatory and technical documentation on labor protection and the environment." Part 1. / E. P. Pyshkina, L. I. Leontieva, M .: Rotaprint MGIU, 1997.

Guidelines for laboratory work"Study of
device and procedure for the use of fire extinguishing means.
B. S. Ivanov, M .: Rotaprint of the Plant-Vtuza at ZIL, 1978.

And Dubina. "Mechanical calculations in Excel 97/2000." - St. Petersburg: BHV - St. Petersburg, 2000.

INTRODUCTION

The revival of Russian industry is the first task of strengthening the country's economy. Without a strong, competitive industry, it is impossible to ensure a normal life for the country and people. Market relations, the independence of factories, the departure from a planned economy dictate to manufacturers to produce products that are in world demand and at minimal cost. The engineering and technical personnel of the plants are entrusted with the task of producing these products at minimal cost in the shortest possible time, with guaranteed quality.

This can be achieved by applying modern technologies for processing parts, equipment, materials, production automation systems and product quality control. The reliability of the machines produced, as well as the economics of their operation, largely depend on the adopted production technology.

The task of improving the technological support of the quality of manufactured machines, and, above all, their accuracy, is urgent. Precision in mechanical engineering is of great importance for improving the operational quality of machines and for the technology of their production. Increasing the accuracy of manufacturing blanks reduces the complexity of machining, and increasing the accuracy of machining reduces the complexity of assembly as a result of eliminating fitting work and ensuring interchangeability of product parts.

Compared with other methods of obtaining machine parts, cutting provides the greatest accuracy and the greatest flexibility of the production process, creates the possibility of the fastest transition from processing workpieces of one size to processing workpieces of another size.

The quality and durability of the tool largely determine the productivity and efficiency of the machining process, and in some cases the general possibility of obtaining parts of the required shape, quality and accuracy. Improving the quality and reliability of the cutting tool contributes to an increase in the productivity of metal cutting.

A reamer is a cutting tool that allows you to obtain high precision of machined parts. It is an inexpensive tool, and labor productivity when working with a reamer is high. Therefore, it is widely used in the finishing of various holes of machine parts. With the modern development of the engineering industry, the range of manufactured parts is huge and the variety of holes requiring reaming is very large. Therefore, designers are often faced with the task of developing a new sweep. A package of applied programs on a computer can help them in this, which calculates the geometry of the cutting tool and displays a working drawing of the sweep on the plotter.

The design sequence and methods for calculating the cutting tool are based both on the general patterns of the design process and on the specific features characteristic of the cutting tool. Each type of tool has design features that must be taken into account when designing.

Specialists who will work in the metalworking industries must be able to competently design various designs of cutting tools for modern metalworking systems, effectively using computer technology (computers) and advances in tool production.

To reduce the time and increase the efficiency of designing a cutting tool, computer-aided calculations are used, the basis of which is software and mathematical software.

The creation of application software packages for calculating the geometric parameters of a complex and especially complex cutting tool on a computer makes it possible to drastically reduce the cost of design labor and improve the quality of designing a cutting tool.

Places, %; Todd - time for rest and personal needs,%; K - coefficient taking into account the type of production; Kz - coefficient taking into account the assembly conditions. For general assembly hydraulic lock time rate: = 1.308 min. Calculation of the required number of assembly stands and its load factors Let's find the estimated number of assembly stands, pcs. \u003d 0.06 pcs. Round up CP = 1. ...

1. Requirements for emissions into the atmosphere.

Protective equipment should limit the presence of harmful substances in the air of the human environment to a level not exceeding the MPC: for each harmful substance, where is the background concentration.

And in the presence of several harmful substances of unidirectional action, the condition (*) in Chapter 1.4 §2. Compliance with these requirements is achieved by localization of harmful substances in the place of their formation by removal from the room or from the equipment and dispersion in the atmosphere. If at the same time the concentration of harmful substances in the atmosphere exceeds the MPC, then the emissions are cleaned from harmful substances in the cleaning devices installed in the exhaust system. The most common are ventilation, technological and conveyor exhaust systems.

In practice, the following options for protecting atmospheric air are implemented:

a) removal of toxic substances from the premises by general ventilation;

b) localization of toxic substances in the zone of their formation local ventilation, purification of polluted air in special devices and its return to industrial premises, if the air meets the regulatory requirements for supply air;

c) localization of toxic substances in the zone of their formation by local ventilation, purification of polluted air in special devices, release and dispersion in the atmosphere;

d) purification of technological gas emissions in special devices, emission and dispersion in the atmosphere; in some cases, exhaust gases are diluted with atmospheric air before being released;

e) purification of exhaust gases in special apparatus and release into the atmosphere or production area.

To comply with the MPC of harmful substances in the atmospheric air of populated areas, the maximum allowable emission (MPE) of harmful substances from systems is established. exhaust ventilation, various technological and power installations. The maximum permissible emissions of gas turbine engines of civil aviation aircraft are determined by GOST 17.2.2.04 - 86; emissions of vehicles with internal combustion engines GOST 17.2.2.03 - 87, etc.; for industrial enterprises MPE is established by the requirements of GOST 17.2.3.02 - 78.

2. Dissipation of emissions in the atmosphere.

The main document regulating the calculation of dispersion and determination of surface concentrations of emissions from industrial enterprises is the “Methodology for calculating the concentration in the atmospheric air of harmful substances contained in emissions from enterprises OND - 86.

When determining the MPE of an impurity from a calculated source, it is necessary to take into account its concentration in the atmosphere, due to emissions from other sources. For cases of dissipation of heated emissions through a single unshaded pipe:

, where

H- pipe height;

Q- the volume of the consumed gas-air mixture ejected through the pipe;

This is the difference between the temperature of the emitted gas-air mixture and the temperature of the ambient atmospheric air, equal to the average temperature of the hottest month at 13:00;

BUT is a coefficient that depends on the temperature gradient of the atmosphere and determines the conditions for vertical and horizontal dispersion of harmful substances.

K F- coefficient taking into account the settling rate of suspended particles of the emission in the atmosphere;

m and n are dimensionless coefficients that take into account the conditions for the exit of the gas-air mixture from the mouth of the pipe.

3. Emission treatment equipment.

Devices for cleaning ventilation and technological emissions into the atmosphere are divided into:

a) dust collectors (dry, electric, filters, wet);

b) mist eliminators (low and high speed);

c) apparatus for capturing vapors and gases (absorption, chemisorption, adsorption and neutralizers);

d) multi-stage cleaning devices (dust and gas traps, mists and solid impurities traps, multi-stage dust traps).

Their work is characterized by a number of key parameters:

a) cleaning efficiency: , where

and - mass concentrations of impurities in the gas before and after the apparatus.

b) hydraulic resistance of cleaning devices: , where

and - pressure of the gas flow at the inlet and outlet of the apparatus;

The coefficient of hydraulic resistance of the apparatus;

and are the density and velocity of the gas in the calculated section of the apparatus.

The value is calculated experimentally, or by this formula.

c) power consumption of the gas movement stimulator: , where

Q - volumetric flow rate of the purified gas;

k - power reserve factor

- efficiency of power transfer from the electric motor to the fan;

fan efficiency.

    The main ways to protect the atmosphere from industrial pollution.

    Purification of technological and ventilation emissions. Purification of exhaust gases from aerosols.

1. The main 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;

    Improvement of technological processes and development of new equipment with a lower level of emissions of impurities and waste into the environment;

    Ecological expertise of all types of industries and industrial products;

    Replacement of toxic wastes with non-toxic ones;

    Replacement of non-recyclable wastes with recycled ones;

    Wide application additional methods and means of environmental protection.

As additional means of environmental protection apply:

    devices and systems for purification of gas emissions from impurities;

    the transfer of industrial enterprises from large cities to sparsely populated areas with unsuitable and unsuitable lands for agriculture;

    the 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 humans and plants;

    organization of 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 should be selected taking into account the aeroclimatic characteristics and terrain.

The industrial facility should be located on a flat, elevated place, well blown by the winds.

The residential site should not be higher than the site of the enterprise, otherwise the advantage of high pipes for dissipating industrial emissions is almost negated.

The mutual location of enterprises and settlements is determined by the average wind rose of the warm period of the year. Industrial facilities that are sources of emissions of harmful substances into the atmosphere are located outside the settlements and on the leeward side of residential areas.

The requirements of the Sanitary Standards for the Design of Industrial Enterprises SN  245  71 stipulate that facilities that are sources of harmful and odorous substances should be separated from residential buildings by sanitary protection zones. The dimensions of these zones are determined depending on:

    enterprise capacity;

    conditions for the implementation of the technological process;

    the nature and quantity of harmful and unpleasantly smelling substances released into the environment.

Five sizes of sanitary protection zones have been established: for enterprises of class I - 1000 m, class II - 500 m, class III - 300 m, class IV - 100 m, class V - 50 m.

According to the degree of impact on the environment, machine-building enterprises 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 Gosstroy of Russia in the presence of unfavorable aerological conditions for dispersing industrial emissions in the atmosphere or in the absence or insufficient efficiency of treatment facilities.

The size of the sanitary protection zone can be reduced by changing technology, improving the technological process and introducing highly efficient and reliable cleaning devices.

The sanitary protection zone may not be used to expand the industrial site.

It is allowed to place objects of a lower hazard class than the main production, fire station, garages, warehouses, office buildings, research laboratories, parking lots, etc.

The sanitary protection zone should be landscaped and landscaped with gas-resistant species of trees and shrubs. From 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.

Control of air pollution in Russia is carried out in almost 350 cities. The monitoring system includes 1200 stations and covers almost all cities with a population of more than 100 thousand inhabitants and cities with large industrial enterprises.

Means of protection of the atmosphere should limit the presence of harmful substances in the air of the human environment at a level not exceeding the MPC. In all cases, the condition must be met:

C+sf MPC(1)

for each harmful substance (sf - background concentration).

Compliance with this requirement is achieved by localization of harmful substances at the place of their formation, removal from the room or equipment and dispersion in the atmosphere. If at the same time the concentration of harmful substances in the atmosphere exceeds the MPC, then the emissions are cleaned from harmful substances in the cleaning devices installed in the exhaust system. The most common are ventilation, technological and transport exhaust systems.

In practice, the following options for protecting atmospheric air are implemented:

  • - removal of toxic substances from the premises by general ventilation;
  • - localization of toxic substances in the zone of their formation by local ventilation, purification of polluted air in special devices and its return to the production or amenity premises, if the air after cleaning in the device meets the regulatory requirements for supply air;
  • - localization of toxic substances in the zone of their formation by local ventilation, purification of polluted air in special devices, emission and dispersion in the atmosphere;
  • - purification of technological gas emissions in special devices, emission and dispersion in the atmosphere; in some cases, exhaust gases are diluted with atmospheric air before being released;
  • - purification of exhaust gases from power plants, for example, internal combustion engines in special units, and release into the atmosphere or production area (mines, quarries, storage facilities, etc.)

To comply with the MPC of harmful substances in the atmospheric air of populated areas, the maximum allowable emission (MAE) of harmful substances from exhaust ventilation systems, various technological and power plants is established.

Devices for cleaning ventilation and technological emissions into the atmosphere are divided into: dust collectors (dry, electric, filters, wet); mist eliminators (low and high speed); devices for capturing vapors and gases (absorption, chemisorption, adsorption and neutralizers); multi-stage cleaning devices (dust and gas traps, mists and solid impurities traps, multi-stage dust traps). Their work is characterized by a number of parameters. The main ones are cleaning activity, hydraulic resistance and power consumption.

Cleaning efficiency

\u003d (svh - svh) / svh (2)

where svh and svh - mass concentrations of impurities in the gas before and after the apparatus.

Dry dust collectors - cyclones of various types have been widely used for cleaning gases from particles.

Electric cleaning (electrostatic precipitators) is one of the most advanced types of gas cleaning from dust and fog particles suspended in them. This process is based on the impact ionization of gas in the zone of the corona discharge, the transfer of the ion charge to impurity particles and the deposition of the latter on the collecting and corona electrodes. For this, electrofilters are used.

For highly efficient cleaning of emissions, it is necessary to use multi-stage cleaning devices. In this case, the gases to be purified sequentially pass through several autonomous purification apparatuses or one unit, which includes several purification stages.

Such solutions are used in highly efficient gas purification from solid impurities; with simultaneous purification from solid and gaseous impurities; when cleaning from solid impurities and dropping liquid, etc. Multi-stage cleaning is widely used in air purification systems with its subsequent return to the room.

Methods for cleaning gas emissions into the atmosphere

The absorption method of gas purification, carried out in absorber units, is the simplest and provides a high degree of purification, however, it requires bulky equipment and purification of the absorbing liquid. Based on chemical reactions between a gas, such as sulfur dioxide, and an absorbent suspension (alkaline solution: limestone, ammonia, lime). With this method, gaseous harmful impurities. The latter can be extracted by desorption by heating with water vapor.

The method of oxidation of combustible carbonaceous harmful substances in the air consists in combustion in a flame and the formation of CO2 and water, the thermal oxidation method consists in heating and feeding into a fire burner.

Catalytic oxidation using solid catalysts is that sulfur dioxide passes through the catalyst in the form of manganese compounds or sulfuric acid.

Reducing agents (hydrogen, ammonia, hydrocarbons, carbon monoxide) are used to purify gases by catalysis using reduction and decomposition reactions. Neutralization of nitrogen oxides NOx is achieved by using methane, followed by the use of aluminum oxide to neutralize the resulting carbon monoxide in the second stage.

A sorption-catalytic method for purifying especially toxic substances at temperatures below the catalysis temperature is promising.

The adsorption-oxidation method also seems to be promising. It consists in the physical adsorption of small amounts of harmful components, followed by the blowing of the adsorbed substance with a special gas flow into a thermocatalytic or thermal afterburning reactor.

In large cities, to reduce the harmful effects of air pollution on humans, special urban planning measures are used: zonal development of residential areas, when low buildings are located close to the road, then tall buildings and under their protection - children's and medical institutions; transport interchanges without intersections, landscaping.

Atmospheric air protection

Atmospheric air is one of the main vital elements of the environment.

The Law “O6 for the Protection of Atmospheric Air” comprehensively covers the problem. He summarized the requirements developed in previous years and justified themselves in practice. For example, the introduction of rules prohibiting the commissioning of any production facilities (newly created or reconstructed) if they become sources of pollution or other negative impacts to atmospheric air. Got further development rules on the regulation of maximum permissible concentrations of pollutants in the atmospheric air.

The state sanitary legislation only for atmospheric air established MPCs for most chemicals with isolated action and for their combinations.

Hygienic standards are a state requirement for business leaders. Their implementation should be monitored by the state sanitary supervision bodies of the Ministry of Health and the State Committee for Ecology.

Of great importance for the sanitary protection of atmospheric air is the identification of new sources of air pollution, the accounting of designed, under construction and reconstructed facilities that pollute the atmosphere, control over the development and implementation of master plans for cities, towns and industrial centers in terms of locating industrial enterprises and sanitary protection zones.

The Law "On the Protection of Atmospheric Air" provides for the requirements to establish standards for maximum permissible emissions of pollutants into the atmosphere. Such standards are established for each stationary source of pollution, for each model of vehicles and other mobile vehicles and installations. They are determined in such a way that the total harmful emissions from all sources of pollution in the area did not exceed the MPC standards for pollutants in the air. Maximum allowable emissions are set only taking into account the maximum allowable concentrations.

The requirements of the Law relating to the use of plant protection products, mineral fertilizers and other preparations are very important. All legislative measures constitute a preventive system aimed at preventing air pollution.

The law provides not only control over the fulfillment of its requirements, but also responsibility for their violation. A special article defines the role public organizations and citizens in the implementation of measures to protect the air environment, obliges them to actively assist state bodies in these matters, since only broad public participation will make it possible to implement the provisions of this law. So, it says that the state gives great importance preservation of the favorable state of atmospheric air, its restoration and improvement to ensure best conditions people's lives - their work, life, recreation and health protection.

Enterprises or their individual buildings and structures, technological processes which are a source of release of harmful and unpleasantly smelling substances into the atmospheric air, are separated from residential buildings by sanitary protection zones. The sanitary protection zone for enterprises and facilities can be increased, if necessary and properly justified, by no more than 3 times, depending on the following reasons: a) the effectiveness of the methods for cleaning emissions into the atmosphere provided or possible for implementation; b) lack of ways to clean emissions; c) placement of residential buildings, if necessary, on the leeward side in relation to the enterprise in the zone of possible air pollution; d) wind roses and other unfavorable local conditions (for example, frequent calms and fogs); e) the construction of new, still insufficiently studied, harmful in sanitary terms, industries.

Sizes of sanitary protection zones for individual groups or complexes of large enterprises in the chemical, oil refining, metallurgical, machine-building and other industries, as well as thermal power plants with emissions that create large concentrations of various harmful substances in the air and have a particularly adverse effect on health and sanitary - hygienic living conditions of the population are established in each specific case by a joint decision of the Ministry of Health and the Gosstroy of Russia.

To increase the effectiveness of sanitary protection zones, trees, shrubs and herbaceous vegetation is planted on their territory, which reduces the concentration of industrial dust and gases. In the sanitary protection zones of enterprises that intensively pollute the atmospheric air with gases harmful to vegetation, the most gas-resistant trees, shrubs and grasses should be grown, taking into account the degree of aggressiveness and concentration of industrial emissions. Particularly harmful to vegetation are emissions from chemical industries (sulphurous and sulfuric anhydride, hydrogen sulfide, sulfuric, nitric, fluoric and bromous acids, chlorine, fluorine, ammonia, etc.), ferrous and non-ferrous metallurgy, coal and thermal power industries.