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Atmosphere protection
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 gas emissions in the atmosphere;
– compliance with standards for permissible emissions of harmful substances;
– arrangement of sanitary protection zones, architectural and planning solutions, etc.
Greening technological processes– this is, first of all, 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, use hydrodust removal, recirculate gases, convert various units to electricity, etc.
The most urgent task of our time is to reduce atmospheric air pollution from exhaust gases from cars. Currently, an active search is underway for an alternative, more “environmentally friendly” fuel than gasoline. Development of car engines running on electricity, solar energy, alcohol, hydrogen, etc. continues.
Purification of gas emissions from harmful impurities. The current level of technology does not allow us to completely prevent the entry of harmful impurities into the atmosphere through gas emissions. Therefore, various methods for purifying exhaust gases from aerosols (dust) and toxic gas and vapor impurities (NO, NO2, SO2, SO3, etc.) are widely used.
To purify emissions from aerosols, various types of devices are used depending on the degree of dust in the air, the size of solid particles and the required level of purification: dry dust collectors(cyclones, dust settling chambers), wet dust collectors(scrubbers, etc.), filters, electrostatic precipitators(catalytic, absorption, adsorption) and other methods for purifying gases from toxic gas and vapor impurities.
Dispersion of gaseous impurities in the atmosphere – this is a reduction of their dangerous concentrations to the level of the corresponding maximum permissible concentration by dispersing dust and gas emissions using high chimneys. The higher the pipe, the greater its dissipative effect. Unfortunately, this method reduces local pollution, but at the same time regional pollution appears.
Construction 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 home is within the sanitary protection zone, defending their constitutional right to a favorable environment, can demand either the cessation of the environmentally hazardous activities of the enterprise, or relocation at the expense of the enterprise outside the sanitary protection zone.
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.
Mist 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 cleaning efficiency equal to 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;
The party and government are constantly concerned about environmental protection, since this problem is inextricably linked with improving the health, prolonging the life and working capacity of Soviet people. [In recent years, enterprises in various industries have put into operation many advanced technological processes, thousands of gas cleaning and dust collection devices and installations that sharply reduce or eliminate emissions of harmful substances into the atmosphere. A program to convert enterprises and boiler houses to natural gas is being implemented on a large scale. Dozens of enterprises and workshops with dangerous sources of air pollution have been moved outside the cities. All this has led to the fact that in most industrial centers and populated areas of the country the level of pollution has noticeably decreased. The number of industrial enterprises equipped with the latest and expensive gas cleaning equipment is also growing.
For the first time in the world, the Soviet Union began to standardize maximum permissible concentrations of harmful substances in the environment. Of course, it would be better to ban polluting the atmosphere altogether, but with the current level of technological processes this is not yet possible. The USSR introduced the world's strictest maximum permissible concentrations of harmful substances in the atmosphere.
Hygienists proceed from the fact that the maximum permissible concentrations of these substances in the air will not have a negative impact on humans and nature.
Hygienic standards are a state requirement for business managers. Their implementation is monitored by the state sanitary supervision bodies of the USSR Ministry of Health and the State Committee for Hydrometeorology and Natural Environment Control.
In 1980, a large and important work was completed in Belarus to inventory the sources of emissions of harmful substances into the atmosphere. The results of the inventory are the basis for the development of standards for maximum permissible emissions at each industrial enterprise. The measures taken made it possible to reduce or stabilize air pollution in many cities of the republic.
Maximum permissible emissions are necessarily established taking into account maximum permissible concentrations.
Sanitary supervision of air cleanliness is one of the important elements of the system for protecting atmospheric air from pollution.
The functions of state sanitary supervision are defined by the “Fundamentals of the Legislation of the USSR and Union Republics on Health Care” (1970) and the “Regulations on State Sanitary Supervision in the USSR”.
Of great importance for the sanitary protection of atmospheric air are the identification of new sources of air pollution, accounting for designed, constructed and reconstructed facilities that pollute the atmosphere, control over the development and implementation of master plans for cities, towns and industrial hubs regarding the location of industrial enterprises and sanitary protection zones.
The Sanitary and Epidemiological Service supervises new construction and reconstruction of industrial facilities, the design and construction of gas and dust treatment facilities at existing enterprises, and inspection of design institutes. Supervision of changes in the technological profile of enterprises.
Our country consistently takes extensive measures to protect the environment. Since January 1981, the Law on the Protection of Atmospheric Air came into force; another real embodiment of the policy of the party and state in this area. It comprehensively covers an important universal problem, systematizing legal norms that have stood the test of time.
The law, first of all, expressed in a more qualified manner those requirements that were developed in previous years and justified themselves in practice. This includes, in particular, rules prohibiting the commissioning of any production facilities - newly created or reconstructed, if during operation they become sources of pollution or other negative impacts on the atmospheric air (Article 13). The rules on standardization of maximum permissible concentrations (MACs) of pollutants in the atmospheric air are maintained and further developed.
At the same time, the law contains a lot of new things. First of all, it should be emphasized that while maintaining the principles of standardization of maximum permissible concentrations of pollutants, the scope of their action is expanding: - MACs will henceforth apply not only in the territory of populated areas, as was previously the case, but throughout the entire territory of the USSR.
Essentially new is the provision provided for in Article 10 on the regulation of maximum permissible emissions of pollutants into the atmosphere by stationary and mobile sources of pollution. This means that for each emission point, say each pipe, a permit will be issued (or not issued) by the competent government authorities, providing for maximum quantities of pollutants released per unit of time. And if this norm specified in the emission permit is violated, then the created situation will naturally be considered an offense with all the ensuing consequences.
This formulation of the issue fully meets the interests of people and the requirements of environmental protection. But in order to strictly comply with these standards, you need to know exactly the composition and amount of harmful substances emitted by every enterprise, every boiler room, every car. First of all, it is planned to conduct an inventory of emission sources, determine the composition and quantity of harmful substances, their concentration in the air, soil, snow cover, and establish distribution boundaries.
Until now, legislation, as is known, is based on the need to protect atmospheric air mainly from pollution and only within populated areas. However, this concept no longer meets the needs of practice. In modern conditions, the atmosphere needs to be protected not only from pollution, although this continues to be the main problem, but also from other types of negative impacts of society, which may result in uncomfortable living conditions for people on Earth. That is why the articles contained in the law on regulating the impact on weather and climate (Article 20), on regulating the consumption of atmospheric air for industrial and other economic needs (Article 19), on preventing, reducing and eliminating the harmful effects on the atmosphere of physical factors (Article 18), etc.
So far, deliberate human influence on the weather is usually limited to the destruction of hail clouds and attempts to artificially cause rain in the desired area. But even these attempts require great caution, because the destruction of a hail cloud in one place can cause a catastrophic downpour in another. The wider use of weather modification poses the risk of other consequences unforeseen today. Taking these circumstances into account, the law provides for a permitting procedure for artificial changes in the state of the atmosphere and atmospheric phenomena.
It is necessary to emphasize the novelty of the rule contained in Article 14 of the law: to prohibit the introduction into practice of discoveries, inventions, rationalization proposals and new technical systems, as well as the acquisition abroad, commissioning and use of technological processes, equipment and other objects if they do not satisfy the established in the USSR requirements for air protection. It is necessary to take into account the requirements of the law on atmospheric air protection when using plant protection products, mineral fertilizers and other preparations. It is easy to see that all these legislative measures constitute a preventive system aimed primarily at preventing air pollution.
The law provides not only for control over its requirements, but also for penalties for violating them.
A special article of the law defines the role of public organizations and citizens in the implementation of measures to protect the air environment, obliging them to actively assist government agencies in these matters. It cannot be otherwise, because only broad public participation will allow the provisions of the law to be implemented.
It is no coincidence that Article 7 obliges government bodies to fully take into account proposals from public organizations and citizens aimed at protecting the atmosphere.
It is difficult to overestimate the educational significance of the new law. Like other laws in force in our country, it develops in every citizen a respectful, caring attitude towards the environment, and teaches us all appropriate behavior.
Cleaning up emissions into the atmosphere. Gas cleaning technology has a variety of methods and devices for removing dust and harmful gases. The choice of method for purifying gaseous impurities is determined primarily by the chemical and physicochemical properties of this impurity. The choice of method is greatly influenced by the nature of production: the properties of the substances available in production, their suitability as gas absorbers, the possibility of recovery (collection and use of waste products) or disposal of captured products.
To purify gases from sulfur dioxide, hydrogen sulfide and methyl mercaptan, neutralization with an alkali solution is used. The result is salt and water.
To purify gases from minor concentrations of impurities (no more than 1% by volume), direct-flow compact absorption devices are used.
Along with liquid absorbers - absorbents - solid absorbers can be used for purification, as well as for drying (dehydration) of gases. These include various brands of active carbons, silica gel, aluminum gel, and zeolites.
Recently, ion exchangers have been used to remove gases with polar molecules from a gas flow. Gas purification processes with adsorbents are carried out in periodic or continuous adsorbers.
To purify the gas stream, dry and wet oxidation processes, as well as catalytic transformation processes, can be used; in particular, catalytic oxidation is used to neutralize sulfur-containing gases of sulfate-cellulose production (gases from cooking and evaporation shops, etc.). This process is carried out at a temperature of 500 - 600 ° C on a catalyst, which contains oxides of aluminum, copper, vanadium and other metals. Organosulfur substances and hydrogen sulfide are oxidized to a less harmful compound - sulfur dioxide (MPC for sulfur dioxide is 0.5 mg/m3, and for hydrogen sulfide is 0.078 mg/m3).
The Kiev Khimvolokno plant operates a unique comprehensive system for purifying ventilation emissions from viscose production. This is a complex set of mechanisms, compressor units, pipelines, and huge absorption tanks. Every day, 6 million m3 of exhaust air passes through the machine “lungs”, and not only cleaning is carried out, but also regeneration.
Until now, at the plant’s viscose production, a significant portion of carbon disulfide was released into the atmosphere. The cleaning system not only protects the environment from pollution, but also saves valuable material.
Electrical precipitators are widely used to remove dust from emissions from thermal power plants. "These are structures with a height of 10-15 storey buildings. They capture fly ash generated by the combustion of solid fuel. Specialists are working to improve the designs of these devices, increasing their efficiency and reliability. The latter The sample is designed to produce more than a million cubic meters of gas per hour, which is used as a raw material for the production of building materials.
Waste-free production. Low-waste and non-waste technological processes make it possible to reduce or completely eliminate environmental pollution, make fuller use of mineral resources, ensure comprehensive processing of primary raw materials and waste dumps of industrial enterprises, obtain additional products and thereby increase the efficiency of the national economy.
Enormous amounts of money are spent on atmospheric air protection. The cost of treatment facilities of many enterprises reaches a third of fixed production assets, and in some cases - 40 - 50%. These costs will increase even more in the future.
What is the way out? He is. It is necessary to look for ways to develop industry and achieve a clean atmosphere that do not exclude each other and do not cause an increase in costs for treatment facilities.
One of these ways is the transition to a fundamentally new waste-free production technology, to the integrated use of raw materials.
Waste-free production technology is a new stage in the development of the scientific and technological revolution. Modern science and technology provide opportunities to overcome the contradictions that arise between outdated production methods and the desire to free the natural environment from harmful influences.
Plants and factories based on zero-waste technology are, in general, the industry of the future. But such enterprises already exist, for example, in the light and food industries. There are a number of enterprises and low-waste production. The Orenburg gas field began to produce by-products - hundreds of thousands of tons of sulfur. The Kirovokan Chemical Plant named after Myasnik has stopped releasing mercury gases into the atmosphere. They are reintroduced into the technological cycle as cheap raw materials for the production of ammonia and urea. Together with them, the most harmful substance - carbon dioxide, which makes up 60% of all plant emissions, no longer enters the air basin.
Enterprises for the integrated use of raw materials provide society with enormous benefits: the efficiency of capital investments sharply increases and the costs of constructing expensive treatment facilities are just as sharply reduced. After all, complete processing of raw materials at one enterprise is always cheaper than obtaining the same products at different ones. And waste-free technology eliminates the danger of environmental pollution. The use of natural resources becomes rational and reasonable.
The history of the ancient world tells us about fire worshipers who prayed to the flame. Metallurgists can also be called “fire worshipers.” Pyrometallurgy (from the ancient Greek “pyre” - fire), which is based on the effect of high temperatures on ores and concentrates, leads to atmospheric pollution and often does not allow for the comprehensive use of raw materials.
In our country, a lot is being done to reduce the risk of environmental pollution from waste from traditional metallurgical industries, and here the future lies in fundamentally new solutions.
On the iron ores of the Kursk magnetic anomaly, the Oskolsky Electrometallurgical Plant is being built - the first domestic enterprise in coke-free metallurgy. This production method sharply reduces harmful emissions into the atmosphere and opens up new prospects for producing high-quality steels. At the Oskol Electrometallurgical Plant, a new technological scheme for the domestic ferrous metallurgy will be used: metallization - electric smelting. The roasted pellets obtained from rich iron ore concentrates are metallized in twelve shaft furnaces (Fig. 18), in which iron oxides are reduced by gas heated to 850 °C - a mixture of CO and H2.
Since cast iron can be dispensed with to produce high-quality steel, this means that the blast furnace process with its expensive and bulky equipment, which pollutes the air, becomes unnecessary.
The new technology has another important advantage: direct reduction of iron in the stream makes it possible to do without coke. This means that the development of metallurgy will not be hampered by a reduction in coking coal reserves.
The problem with waste is not only that it pollutes the biosphere, but also that raw materials are not used comprehensively.
At Ural non-ferrous metallurgy enterprises alone, when smelting copper from copper-zinc concentrates with waste slag and dust, 70 thousand tons of zinc are lost annually. In addition to zinc, the ore contains sulfur and iron. By the way, 50 - 60% of the value of many copper ores comes from sulfur and another 10 - 12% from iron.
At the Irtysh polymetallic plant named after the 50th anniversary of the Kazakh SSR, a KIVCET unit operates. Behind this name is a fundamentally new process for producing non-ferrous metals - oxygen-suspended cyclone-electrothermal smelting. The purpose of the process is to combine in one unit all operations from the preparation of ore, the output of the finished metal, using sulfur previously emitted into the atmosphere as fuel.
The most difficult thing is to move away from tradition, to overcome the inertia of thinking. Non-ferrous metallurgy has existed for eight thousand years. From time immemorial, proven technological processes have come to us and have already become canonical. It was unthinkable to imagine the plant without the gloomy “umbrellas” of toxic smoke.
The main “participants” of the new process are oxygen and electricity. Accordingly, the unit itself consists of two zones. The first involves ore preparation and smelting. Instead of coke, the fuel here is sulfur contained in the ore itself. It burns completely in oxygen, releasing a large amount of heat. And then the melt enters the second zone and flows between the electrodes, breaking up into its component parts. Some metals, zinc for example, evaporate and then condense in their pure form, others are released directly into the ladle. KIVTSET allows you to extract literally everything that is in it from ore. Thus, the plant produces from raw materials not only traditional metals such as copper, lead, zinc, but also cadmium and rare metals.
So far, with the help of KIVCET, the same copper is obtained as in shaft furnaces. The metal needs additional processing. In the future, it is planned to “train” the unit to smelt pure copper.
KIVCET is patented in the USA, Germany, France, etc. - in 18 countries. Metallurgists are attracted to it not only by its ease of use and maintenance, not only by the ability to automate the complex and labor-intensive process of metal smelting, not only by the absence of harmful emissions, but also, first of all, by its unpretentiousness: after all, it is capable of processing raw materials that were previously considered waste - with content metal is 6 - 7 times lower than normal. No other technology will take such raw materials. Moreover, there is much less metal waste in the slag than in the conventional process.
In November 1979, a pan-European high-level meeting on cooperation in the field of environmental protection was held in Geneva. Almost all European countries, as well as the USA and Canada are represented there. The meeting adopted a Declaration on low-waste and waste-free technology and waste use.
The Declaration emphasizes the need to protect people and their environment and to use resources sustainably by promoting the development of low- and zero-waste technologies and the use of waste. Reductions in waste and pollutant emissions across production cycles are targeted through the use of improved industrial processes when creating new or refurbishment of existing production facilities, designing products with special consideration to increase their durability, facilitate repair and reuse whenever possible. Of great importance is the regeneration and use of waste, its transformation into a useful product, in particular, by extracting valuable substances and materials from waste gases, better use of the energy contained in waste and residual products. It is important to reuse more waste as secondary raw materials in other production processes. It is recommended to rationally use raw materials in production processes and throughout the entire life cycle of products, replacing depleting raw materials with other available types. It is necessary to rationally use energy resources in the process of energy production and consumption and, if practical, use waste heat.
Much emphasis is placed on assessing industrial scale applications of low-waste and zero-waste technology for optimal use of raw materials and energy, including recovery, recycling and cost-effectiveness, while taking into account environmental and social impacts.
To create waste-free industrial production on a nationwide scale, it is necessary to develop scientific and technical foundations for planning and designing regional territorial-industrial complexes, in which waste from some enterprises could serve as raw materials for others. The introduction of such complexes will inevitably require a restructuring of connections between enterprises and sectors of the national economy and large costs. However, all this will pay off handsomely over time, as the industry will receive a huge influx of previously unused raw materials and materials, not to mention how much cleaner and more harmless the environment around us will become.
Sanitary protection zones. Enterprises, their individual buildings and structures with technological processes that are sources of release of harmful and unpleasant-smelling substances into the atmospheric air are separated from residential buildings by sanitary protection zones.
The size of the sanitary protection zone to the border of residential development is established: a) for enterprises with technological processes that are sources of air pollution with harmful and unpleasant-smelling substances - directly from sources of air pollution concentrated (through pipes, mines) or dispersed emissions (through building lights etc.), as well as from places where raw materials are loaded or open warehouses; b) for thermal power plants, industrial and heating boiler houses - from chimneys.
In accordance with the sanitary classification of enterprises, industries and facilities, the following dimensions of sanitary protection zones for enterprises are established:
Table 3
The original text is available for download on the contents pageSources 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 cloudiness 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.
