Atmospheric protection means. Technical means and methods of protecting the atmosphere Technical means and methods of protecting the atmosphere
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 permissible emission standards 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 electric vehicle engines continues solar energy, alcohol, hydrogen, etc.
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 they are widely used various methods purification of exhaust gases from aerosols (dust) and toxic gas and vapor impurities (NO, NO2, SO2, SO3, etc.).
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 located 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.
Emissions industrial enterprises characterized by a wide variety of dispersed composition and other physicochemical properties. In this regard, various methods for their purification and types of gas and dust collectors - devices designed to purify emissions from pollutants - have been developed.
Methods for cleaning industrial emissions from dust can be divided into two groups: dust collection methods "dry" method and dust collection methods "wet" method. Gas dust removal devices include: dust settling chambers, cyclones, porous filters, electric precipitators, scrubbers, etc.
The most common dry dust collection installations are cyclones various types.
They are used to capture flour and tobacco dust, ash formed when burning fuel in boiler units. The gas flow enters the cyclone through pipe 2 tangentially to the inner surface of housing 1 and performs a rotational-translational motion along the housing. Under the influence of centrifugal force, dust particles are thrown towards the wall of the cyclone and, under the influence of gravity, fall into the dust collection hopper 4, and the purified gas exits through the outlet pipe 3. normal operation The cyclone requires its tightness; if the cyclone is not sealed, then due to the suction of outside air, dust is carried out with the flow through the outlet pipe.
The tasks of cleaning gases from dust can be successfully solved by cylindrical (TsN-11, TsN-15, TsN-24, TsP-2) and conical (SK-TsN-34, SK-TsN-34M, SKD-TsN-33) cyclones, developed by the Research Institute for Industrial and Sanitary Gas Purification (NIIOGAZ). For normal functioning the excess pressure of gases entering the cyclones should not exceed 2500 Pa. In this case, in order to avoid condensation of liquid vapors, the temperature of the gas is selected to be 30 - 50 o C above the t dew point, and according to the conditions of structural strength - no higher than 400 o C. The productivity of the cyclone depends on its diameter, increasing with the growth of the latter. The cleaning efficiency of cyclones of the TsN series decreases with increasing angle of entry into the cyclone. As the particle size increases and the cyclone diameter decreases, the cleaning efficiency increases. Cylindrical cyclones are designed to collect dry dust from aspiration systems and are recommended for use for pre-cleaning of gases at the inlet of filters and electric precipitators. Cyclones TsN-15 are made of carbon or low-alloy steel. Canonical cyclones of the SK series, designed for cleaning gases from soot, have increased efficiency compared to cyclones of the TsN type due to greater hydraulic resistance.
To purify large masses of gases, battery cyclones are used, consisting of a larger number of parallel installed cyclone elements. Structurally, they are combined into one housing and have a common gas supply and outlet. Experience in operating battery cyclones has shown that the cleaning efficiency of such cyclones is somewhat lower than the efficiency of individual elements due to the flow of gases between the cyclone elements. The domestic industry produces battery cyclones such as BC-2, BTsR-150u, etc.
Rotary dust collectors are classified as devices centrifugal action, which simultaneously with the movement of air clean it from the dust fraction larger than 5 microns. They are very compact, because... the fan and dust collector are usually combined in one unit. As a result, during installation and operation of such machines, no additional space is required to accommodate special dust collection devices when moving a dusty stream with an ordinary fan.
The design diagram of the simplest rotary type dust collector is shown in the figure. When the fan wheel 1 operates, dust particles, due to centrifugal forces, are thrown towards the wall of the spiral casing 2 and move along it in the direction of the exhaust hole 3. The dust-enriched gas is discharged through a special dust receiving hole 3 into the dust bin, and the purified gas enters the exhaust pipe 4 .
To increase the efficiency of dust collectors of this design, it is necessary to increase the portable speed of the purified flow in the spiral casing, but this leads to a sharp increase in the hydraulic resistance of the device, or to reduce the radius of curvature of the casing spiral, but this reduces its productivity. Such machines provide a fairly high efficiency of air purification while capturing relatively large dust particles - over 20 - 40 microns.
More promising rotary dust separators, designed to clean air from particles > 5 µm in size, are counter-flow rotary dust separators (RPD). The dust separator consists of a hollow rotor 2 with a perforated surface built into the casing 1 and a fan wheel 3. The rotor and fan wheel are mounted on a common shaft. When the dust separator operates, dusty air enters the housing, where it swirls around the rotor. As a result of the rotation of the dust flow, centrifugal forces arise, under the influence of which suspended dust particles tend to separate from it in the radial direction. However, aerodynamic drag forces act on these particles in the opposite direction. Particles whose centrifugal force is greater than the aerodynamic drag force are thrown toward the walls of the casing and enter hopper 4. The purified air is thrown out through the perforation of the rotor using a fan.
The efficiency of PRP cleaning depends on the selected ratio of centrifugal and aerodynamic forces and theoretically can reach 1.
A comparison of PDPs with cyclones demonstrates the advantages of rotary dust collectors. Thus, the overall dimensions of the cyclone are 3 - 4 times, and the specific energy consumption for purifying 1000 m 3 of gas is 20 - 40% greater than that of the PRP, all other things being equal. However, rotary dust collectors have not become widespread due to the relative complexity of the design and operating process compared to other devices for dry gas purification from mechanical contaminants.
To separate the gas flow into purified gas and dust-enriched gas, use louvered dust separator On the louvre grille 1, the gas flow with flow rate Q is divided into two flow paths with flow rates Q 1 and Q 2. Usually Q 1 = (0.8-0.9)Q, and Q 2 = (0.1-0.2)Q. The separation of dust particles from the main gas flow on the louvre grille occurs under the influence of inertial forces that arise when the gas flow turns at the entrance to the louvre grille, as well as due to the effect of reflection of particles from the surface of the grille upon impact. The dust-enriched gas flow after the louvered grille is directed to a cyclone, where it is cleaned of particles, and is reintroduced into the pipeline behind the louvered grille. Louvre dust separators are simple in design and are well arranged in gas ducts, providing a cleaning efficiency of 0.8 or more for particles larger than 20 microns. They are used for cleaning flue gases from coarse dust at temperatures up to 450 – 600 o C.
Electric precipitator. Electrical cleaning is one of the most advanced types of gas purification from suspended particles of dust and fog. This process is based on impact ionization of gas in the corona discharge zone, transfer of ion charge to impurity particles and deposition of the latter on collecting and corona electrodes. Precipitation electrodes 2 are connected to the positive pole of the rectifier 4 and grounded, and the corona electrodes are connected to the negative pole. The particles entering the electrostatic precipitator are connected to the positive pole of the rectifier 4 and are grounded, and the corona electrodes are charged with ana impurity ions. Usually they already have a small charge obtained due to friction against the walls of pipelines and equipment. Thus, negatively charged particles move towards the collection electrode, and positively charged particles settle on the negative discharge electrode.
Filters widely used for fine purification of gas emissions from impurities. The filtration process consists of retaining impurity particles on porous partitions as they move through them. The filter consists of housing 1, separated by a porous partition (filter-
element) 2 into two cavities. Contaminated gases enter the filter and are cleaned as they pass through the filter element. Impurity particles settle on the inlet part of the porous partition and are retained in the pores, forming layer 3 on the surface of the partition.
According to the type of partitions, filters are: - with granular layers (stationary, freely poured granular materials) consisting of grains of various shapes, used to purify gases from large impurities. To purify gases from dust of mechanical origin (from crushers, dryers, mills, etc.), gravel filters are often used. Such filters are cheap, easy to operate and provide high cleaning efficiency (up to 0.99) of gases from coarse dust.
With flexible porous partitions (fabrics, felts, sponge rubber, polyurethane foam, etc.);
With semi-rigid porous partitions (knitted and woven mesh, pressed spirals and shavings, etc.);
With rigid porous partitions (porous ceramics, porous metals, etc.).
The most widely used in industry for dry purification of gas emissions from impurities are bag filters. The required number of hoses 1 is installed in the filter housing 2, into the internal cavity of which dusty gas is supplied from the incoming pipe 5. Due to sieve and other effects, particles of contaminants settle in the pile and form a dust layer on the inner surface of the hoses. Purified air leaves the filter through pipe 3. When the maximum permissible pressure drop across the filter is reached, it is disconnected from the system and regeneration is carried out by shaking the hoses and blowing them with compressed gas. Regeneration is carried out by a special device 4.
Dust collectors of various types, including electric precipitators, are used at elevated concentrations of impurities in the air. Filters are used for fine air purification with impurity concentrations of no more than 50 mg/m 3; if the required fine air purification occurs at high initial concentrations of impurities, then the purification is carried out in a system of series-connected dust collectors and filters.
Devices wet cleaning gases are widespread, because are characterized by high cleaning efficiency from fine dust with d h ≥ (0.3-1.0) microns, as well as the ability to clean hot and explosive gases from dust. However, wet dust collectors have a number of disadvantages that limit their scope of application: formations during the cleaning process sludge, which requires special systems for its processing; removal of moisture into the atmosphere and formation of deposits in exhaust flues when gases are cooled to the dew point temperature; the need to create circulating systems for supplying water to the dust collector.
Wet cleaning devices operate on the principle of deposition of dust particles onto the surface of either liquid droplets or a liquid film. The deposition of dust particles onto the liquid occurs under the influence of inertial forces and Brownian motion.
Among wet cleaning devices with the deposition of dust particles on the surface of droplets, in practice they are more applicable Venturi scrubbers. The main part of the scrubber is Venturi nozzle 2, into the confuser part of which a dusty gas flow is supplied and liquid is supplied through centrifugal nozzles 1 for irrigation. In the confuser part of the nozzle, gas is accelerated from input speed 15-20 m/s to a speed in the narrow section of the nozzle 30-200 m/s, and in the diffuser part of the nozzle the flow is slowed down to a speed of 15-20 m/s and fed into the droplet eliminator 3. The droplet eliminator is usually made in the form of a direct-flow cyclone. Venturi scrubbers provide high efficiency in cleaning aerosols with an average particle size of 1-2 microns with an initial impurity concentration of up to 100 g/m 3 .
Wet dust collectors include bubbling foam dust collectors with failure and overflow grilles. In such devices, the gas for cleaning enters under the grid 3, passes through the holes in the grid and, passing through a layer of liquid or foam 2, under pressure, is cleaned of part of the dust due to the deposition of particles on the inner surface of gas bubbles. The operating mode of the devices depends on the speed of air supply under the grille. At speeds up to 1 m/s, a bubbling mode of operation of the apparatus is observed. A further increase in gas velocity in the apparatus body from 1 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 splash removal from the apparatus. Modern bubbling-foam devices provide gas purification efficiency from fine dust ≈ 0.95-0.96 at specific costs water 0.4-0.5 l/m3. But these devices are very sensitive to uneven gas supply under the failure grates, which leads to local blowing off of the liquid film from the grate. Grates are prone to clogging.
Methods for purifying industrial emissions from gaseous pollutants, based on the nature of the physical and chemical processes, are divided into five main groups: washing emissions with solvents of impurities (absorption); washing emissions with solutions of reagents that bind impurities chemically (chemisorption); absorption of gaseous impurities by solid active substances (adsorption); thermal neutralization of waste gases and the use of catalytic conversion.
Absorption method. In gas emissions purification technology, the absorption process is often called 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 a liquid absorber (absorbent) to form a solution.
The driving force here is the concentration gradient at the gas-liquid phase boundary. The component of the gas-air mixture (absorbate) dissolved in the liquid penetrates into the internal layers of the absorbent due to diffusion. The process proceeds faster, the larger the phase interface, flow turbulence and diffusion coefficients, i.e. 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. If the solubility of gases at 0°C and a partial pressure of 101.3 kPa is hundreds of grams per 1 kg of solvent, then such gases are called highly soluble.
The organization of contact of the gas flow with the liquid solvent is carried out either by passing the gas through a packed column, or by spraying the liquid, or by bubbling the gas through a layer of absorbent liquid. Depending on the implemented method of gas-liquid contact, the following are distinguished: packed towers: nozzle and centrifugal scrubbers, Venturi scrubbers; bubbling foam and other scrubbers.
The general structure of the counterflow packed tower is shown in the figure. Contaminated gas enters bottom part tower, and the purified one leaves it through top part, where using one or more sprinklers 2
A clean absorbent is introduced, and the waste solution is taken from the bottom. The purified gas is usually released into the atmosphere. 
The liquid leaving the absorber is regenerated, desorbing the contaminant, and returned to the process or removed as a waste (by-product). The chemically inert nozzle 1, filling the internal cavity of the column, is designed to increase the surface of the liquid spreading over it in the form of a film. As a nozzle, bodies of different geometric shapes are used, each of which is characterized by its own specific surface area and resistance to the movement of the gas flow.
The choice of purification method is determined by technical and economic calculations and depends on: the concentration of the pollutant in the gas being purified and the required degree of purification, depending on the background air pollution in a given region; volumes of purified gases and their temperatures; the presence of accompanying gaseous impurities and dust; the need for certain recycling products and the availability of the required sorbent; the size of the areas available for the construction of a gas treatment plant; availability of the necessary catalyst, natural gas, etc.
When choosing hardware design for new technological processes, as well as when reconstructing existing gas purification installations, it is necessary to be guided by the following requirements: maximum efficiency of the purification process in a wide range of load characteristics at low energy costs; simplicity of design and maintenance; compactness and the possibility of manufacturing devices or individual units from polymer materials; possibility of working with circulation irrigation or self-irrigation. The main principle that should be the basis for design treatment facilities, is the maximum possible retention of harmful substances, heat and their return to the technological process.
Task No. 2: At the grain processing enterprise, equipment is installed that is a source of grain dust. To remove it from the working area, the equipment is equipped aspiration system. In order to clean the air before releasing it into the atmosphere, a dust collection unit consisting of a single or battery cyclone is used.
Determine: 1. Maximum permissible emission of grain dust.
2. Select the design of a dust collection installation consisting of cyclones from the Research Institute for Industrial and Sanitary Gas Purification (NII OGAZ), determine its efficiency according to the schedule and calculate the dust concentration at the inlet and outlet of the cyclone.
Emission source height H = 15 m,
The speed of release of the gas-air mixture from the source w o = 6 m/s,
Source mouth diameter D = 0.5 m,
Release temperature Tg = 25 o C,
Ambient air temperature Тв = _ -14 о С,
Average dust particle size d h = 4 µm,
MPC of grain dust = 0.5 mg/m 3,
Background concentration of grain dust C f = 0.1 mg/m 3,
The company is located in the Moscow region,
The terrain is calm.
Solution.1. Determine the maximum permissible value of grain dust:
M pdv = 
, mg/m 3
from the definition of the maximum permissible value we have: C m = C maximum permissible concentration – C f = 0.5-0.1 = 0.4 mg/m 3 ,
Gas-air mixture flow rate V 1 = 
,
DT = Тg – Тв = 25 – (-14) = 39 о С,
determine the emission parameters: f =1000 
, Then
m = 1/(0.67+0.1 + 0.34) = 1/(0.67 + 0.1 +0.34) = 0.8.
V m = 0.65 
, Then
n = 0.532V m 2 – 2.13V m + 3.13= 0.532×0.94 2 – 2.13×0.94 + 3.13 = 1.59, and
M pdv = 
g/s.
2. Selection of a treatment plant and determination of its parameters.
a) The selection of a dust collection unit is made according to catalogs and tables (“Ventilation, air conditioning and air purification at food industry enterprises” E.A. Shtokman, V.A. Shilov, E.E. Novgorodsky et al., M., 1997). The selection criterion is the performance of the cyclone, i.e. the flow rate of the gas-air mixture at which the cyclone has maximum efficiency. To solve the problem, we will use the table:
The first line provides data for a single cyclone, the second - for a battery cyclone.
If the calculated productivity is in the range between the table values, then choose the design of the dust collection installation with the next higher productivity.
We determine the hourly productivity of the treatment plant:
V h = V 1 × 3600 = 1.18 × 3600 = 4250 m 3 / h
According to the table, according to the nearest larger value V h = 4500 m 3 / h, we select a dust collection unit in the form of a single cyclone TsN-11 with a diameter of 800 mm.
b) According to the graph in Fig. 1 of the appendix, the efficiency of the dust collection installation with an average diameter of dust particles of 4 microns is hp = 70%.
c) Determine the dust concentration at the exit from the cyclone (at the mouth of the source):
From out = 
The maximum concentration of dust in the purified air Cin is determined:
C in = 
.
If the actual value of Cin is more than 1695 mg/m 3, then the dust collection installation will not give the desired effect. In this case, more advanced cleaning methods must be used.
3. Determine the pollution indicator
P = 
,
where M is the mass of pollutant emission, g/s,
The pollution indicator shows how much clean air is needed to “dissolve” the pollutant emitted by the source per unit of time to the maximum permissible concentration, taking into account the background concentration.
P = 
.
The annual pollution indicator is the total pollution indicator. To determine it, we find the mass of grain dust emissions per year:
M year = 3.6 × M MPE × T × d ×10 -3 = 3.6 × 0.6 × 8 × 250 × 10 -3 = 4.32 t/year, then
åР = 
.
The pollution indicator is necessary for the comparative assessment of different emission sources.
For comparison, let’s calculate åP for sulfur dioxide from the previous problem for the same period of time:
M year = 3.6 × M MPE × T × d × 10 -3 = 3.6 × 0.71 × 8 × 250 × 10 -3 = 5.11 t/year, then
åР = 
And in conclusion, it is necessary to draw a sketch of the selected cyclone according to the dimensions given in the appendix, on an arbitrary scale.
Pollution control environment. Payment for environmental damage.
When calculating the amount of pollutant, i.e. ejection mass is determined by two values: gross emissions (t/year) and maximum single emissions (g/s). The gross emission value is used for a general assessment of air pollution by a given source or group of sources, and is also the basis for calculating payments for environmental pollution.
The maximum single emission makes it possible to assess the state of atmospheric air pollution at a given time and is the initial value for calculating the maximum surface concentration of a pollutant and its dispersion in the atmosphere.
When developing measures to reduce emissions of pollutants into the atmosphere, it is necessary to know what contribution each source makes to the overall picture of air pollution in the area where the enterprise is located.
TSV – temporarily coordinated release. If at a given enterprise or group of enterprises located in the same area (Normal Physics is large), the MPE value for objective reasons cannot be achieved at the present time, then, in agreement with the body exercising state control over the protection of the atmosphere from pollution, the user of natural resources is assigned an ELV with adoption of a gradual reduction of emissions to MPE values and the development of specific measures for this.
Payments are collected for the following types of harmful effects on the environment: - emission of pollutants into the atmosphere from stationary and mobile sources;
Discharge of pollutants into surface and underground water bodies;
Waste disposal;
Dr. types of harmful effects (noise, vibration, electromagnetic and radiation effects, etc.).
Two types of basic payment standards have been established:
a) for emissions, discharges of pollutants and waste disposal within acceptable standards
b) for emissions, discharges of pollutants and waste disposal within established limits (temporarily agreed standards).
Basic payment standards are established for each pollutant (waste) ingredient, taking into account their degree of danger to the environment and public health.
The rates of payment for pollution of hazardous pollutants are indicated in the Decree of the Government of the Russian Federation of June 12, 2003. No. 344 “On payment standards for emissions of pollutants into the atmospheric air from stationary and mobile sources, discharges of pollutants into surface and underground water bodies, disposal of industrial and consumer waste” for 1 ton in rubles:
Payment for emissions of pollutants that do not exceed the standards established for the user of natural resources:
П = С Н × М Ф, with М Ф £ М Н,
where М Ф – actual emission of pollutant, t/year;
МН – maximum permissible standard for this pollutant;
С Н – rate of payment for the emission of 1 ton of a given pollutant within the limits of permissible emission standards, rubles/t.
Payment for emissions of pollutants within established emission limits:
P = S L (M F – M N) + S N M N, with M N< М Ф < М Л, где
S L – rate of payment for the emission of 1 ton of pollutant within the established emission limits, rub/t;
M L – established emission limit for a given pollutant, t/year.
Payment for excess emissions of pollutants:
P = 5× S L (M F – M L) + S L (M L – M N) + S N × M N, with M F > M L.
Payment for the emission of pollutants when the user of natural resources has not established standards for the emission of pollutants or a fine:
P = 5 × S L × M F
Payments for maximum permissible emissions, pollutant discharges, waste disposal are made at the expense of the cost of products (works, services), and for exceeding them - at the expense of the profit remaining at the disposal of the natural resource user.
Payments for environmental pollution are received:
19% to the Federal Budget,
81% to the budget of the subject of the Federation.
Task No. 3. “Calculation of technological emissions and payment for environmental pollution natural environment using the example of a bakery"
The bulk of pollutants, such as ethyl alcohol, acetic acid, acetaldehyde, are formed in baking chambers, from where they are removed through exhaust ducts due to natural draft or emitted into the atmosphere through metal pipes or shafts with a height of at least 10 - 15 m. Emissions of flour dust mainly occur in flour warehouses. Oxides of nitrogen and carbon are formed when natural gas is burned in baking chambers.
Initial data:
1. Annual production of the Moscow bakery is 20,000 tons/year of bakery products, incl. bakery products from wheat flour - 8,000 t/year, bakery products from rye flour - 5,000 t/year, bakery products from mixed rolls - 7,000 t/year.
2. Roll recipe: 30% - wheat flour and 70% - rye flour
3. The storage condition for flour is bulk.
4. Fuel in furnaces and boilers is natural gas.
I. Technological emissions from the bakery.
II. Payment for air pollution, if the maximum permissible limit is:
Ethyl alcohol – 21t/year,
Acetic acid – 1.5 t/year (VSV – 2.6 t/year),
Acetaldehyde – 1 t/year,
Flour dust – 0.5 t/year,
Nitrogen oxides – 6.2 t/year,
Carbon oxides – 6 t/year.
1. In accordance with the methodology of the All-Russian Research Institute of HP, technological emissions when baking bakery products are determined by the method of specific indicators:
M = B × m, where
M – amount of pollutant emissions in kg per unit of time,
B – production output in tons for the same period of time,
m – specific indicator of pollutant emissions per unit of output, kg/t.
Specific emissions of pollutants in kg/t of finished products.
1.Ethanol: bakery products from wheat flour – 1.1 kg/t,
bakery products made from rye flour – 0.98 kg/t.
2. Acetic acid: bakery products made from wheat flour – 0.1 kg/t,
bakery products made from rye flour – 0.2 kg/t.
3. Acetaldehyde – 0.04 kg/t.
4. Flour dust – 0.024 kg/t (for bulk storage flour), 0.043 kg/t (for container storage of flour).
5. Nitrogen oxides - 0.31 kg/t.
6. Carbon oxides – 0.3 kg/t.
I. Calculation of process emissions:
1. Ethyl alcohol:
M 1 = 8000 × 1.1 = 8800 kg/year;
M 2 = 5000 × 0.98 = 4900 kg/year;
M 3 = 7000(1.1×0.3+0.98×0.7) = 7133 kg/year;
total emission M = M 1 + M 2 + M 3 = 8800 + 4900 + 7133 = 20913 kg/year.
2. Acetic acid:
Bakery products made from wheat flour
M 1 = 8000 × 0.1 = 800 kg/year;
Bakery products made from rye flour
M 2 = 5000 × 0.2 = 1000 kg/year;
Mixed roll baked goods
M 3 = 7000(0.1×0.3+0.2×0.7) = 1190 kg/year,
total emission M = M 1 + M 2 + M 3 = 800 + 1000 + 1190 = 2990 kg/year.
3. Acetaldehyde M = 20000 × 0.04 = 800 kg/year.
4. Flour dust M = 20000 × 0.024 = 480 kg/year.
5. Nitrogen oxides M = 20000 × 0.31 = 6200 kg/year.
6. Carbon oxides M = 20000 × 0.3 = 6000 kg/year.
II. Calculation of fees for pollution of hazardous pollutants.
1. Ethyl alcohol: M H = 21 t/year, M F = 20.913 t/year Þ P = S H × M f = 0.4 × 20.913 = 8.365 rub.
2. Acetic acid: M H = 1.5 t/year, M L = 2.6 t/year, M F = 2.99 t/year Þ P = 5 S L (M F – M L) + S L ( M L – M N)+S N × M N =
5 × 175 × (2.99-2.6) + 175 × (2.6 – 1.5) + 35 × 1.5 = 586.25 rub.
3. Acetic aldehyde: M H = 1 t/year, M F = 0.8 t/year Þ P = C H × M F = 68 × 0.8 = 54.4 rubles.
4. Flour dust: M N = 0.5 t/year, M F = 0.48 t/year Þ P = S N × M F = 13.7 × 0.48 = 6.576 rubles.
5. Nitrogen oxide: M N = 6.2 t/year, M F = 6.2 t/year Þ P = S N × M F = 35 × 6.2 = 217 rub.
6. Carbon oxide: M H = 6 t/year, M F = 6 t/year Þ
P = S N × M F = 0.6 × 6 = 3.6 rub.
Coefficient taking into account environmental factors, for the Central region of the Russian Federation = 1.9 for atmospheric air, for the city the coefficient is 1.2.
åП = 876.191 · 1.9 · 1.2 = 1997.72 rubles
CONTROL TASKS.
Exercise 1
| Option No. | Boiler room productivity Q about, MJ/hour | Source height H, m | Mouth diameter D, m | Background concentration of SO 2 C f, mg/m 3 |
| 0,59 | 0,004 | |||
| 0,59 | 0,005 | |||
| 0,6 | 0,006 | |||
| 0,61 | 0,007 | |||
| 0,62 | 0,008 | |||
| 0,63 | 0,004 | |||
| 0,64 | 0,005 | |||
| 0,65 | 0,006 | |||
| 0,66 | 0,007 | |||
| 0,67 | 0,008 | |||
| 0,68 | 0,004 | |||
| 0,69 | 0,005 | |||
| 0,7 | 0,006 | |||
| 0,71 | 0,007 | |||
| 0,72 | 0,008 | |||
| 0,73 | 0,004 | |||
| 0,74 | 0,005 | |||
| 0,75 | 0,006 | |||
| 0,76 | 0,007 | |||
| 0,77 | 0,008 | |||
| 0,78 | 0,004 | |||
| 0,79 | 0,005 | |||
| 0,8 | 0,006 | |||
| 0,81 | 0,007 | |||
| 0,82 | 0,008 | |||
| 0,83 | 0,004 | |||
| 0,84 | 0,005 | |||
| 0,85 | 0,006 | |||
| 0,86 | 0,007 | |||
| 0,87 | 0,004 | |||
| 0,88 | 0,005 | |||
| 0,89 | 0,006 |
To purify gases from harmful gaseous impurities, two groups of methods are used - non-catalytic and catalytic. Methods of the first group are based on removing impurities from a gaseous mixture using liquid absorbers) and solid (adsorbers) absorbers. Methods of the second group consist in the fact that harmful impurities enter chemical reaction and are converted into harmless substances on the surface of the catalysts. An even more complex and multi-stage process is wastewater treatment.
All known methods and means of protecting the atmosphere from chemical impurities can be combined into three groups.
The first group includes measures aimed at reducing emission power, i.e. reduction in the amount of emitted substance per unit time. The second group includes measures aimed at protecting the atmosphere by processing and neutralizing harmful emissions with special cleaning systems. The third group includes measures to regulate emissions, both individual enterprises and devices, and in the region as a whole.
To reduce the power of emissions of chemical impurities into the atmosphere, the following are most widely used:
- - replacement of less environmentally friendly fuels with environmentally friendly ones;
- - fuel combustion using special technology;
- - creation of closed production cycles.
Absorption methods for purifying waste gases are divided according to the following characteristics:
- 1) according to the absorbed component;
- 2) by the type of absorbent used;
- 3) by the nature of the process - with and without gas circulation;
- 4) on the use of the absorbent - with regeneration and its return to the cycle (cyclic) and without regeneration (non-cyclic);
- 5) on the use of recovered components - with and without recovery;
- 6) by type of recovered product;
- 7) on the organization of the process - periodic and continuous;
- 8) by structural types absorption equipment.
For physical absorption, in practice, water, organic solvents that do not react with the extracted gas, and aqueous solutions of these substances are used. In chemisorption, aqueous solutions of salts and alkalis, organic substances and aqueous suspensions of various substances are used as absorbents.
The choice of cleaning method depends on many factors; concentration of the extracted component in the exhaust gases, gas volume and temperature, impurity content, presence of chemisorbents, possibility of using recovery products, required degree of purification. The choice is made based on the results of technical and economic calculations.
Adsorption methods of gas purification are used to remove gaseous and vapor impurities from them. The methods are based on the absorption of impurities by porous adsorbent bodies. Cleaning processes are carried out in batch or continuous adsorbers. The advantage of the methods is high degree cleaning, but the disadvantage is the impossibility of cleaning dusty gases.
Catalytic purification methods are based on the chemical transformation of toxic components into non-toxic ones on the surface of solid catalysts. Gases that do not contain dust and catalyst poisons are subjected to purification. The methods are used to purify gases from nitrogen oxides, sulfur, carbon and organic impurities. They are carried out in reactors various designs.
In recovery technology, along with other methods, condensation and compression methods are used to capture vapors of volatile solvents.
The condensation method is based on the phenomenon of a decrease in the saturated vapor pressure of the solvent with decreasing temperature. The mixture of solvent vapor and air is pre-cooled in a heat exchanger and then condensed. The advantages of the method are the simplicity of the hardware design and operation of the recovery unit. However, the process of purifying steam-air mixtures by condensation is very complicated, since the content of volatile solvent vapors in these mixtures usually exceeds their lower explosive limit. The disadvantages of the method also include high costs refrigerant and electricity and a low percentage of vapor condensation (yield) of solvents - usually does not exceed 70-90%. The condensation method is cost-effective only if the solvent vapor content in the stream being purified is 100 g/m 3 , which significantly limits the scope of application of condensation-type installations.
The compression method is based on the same phenomenon as the condensation method, but in relation to solvent vapors under overpressure. However, the compression method is more complex in hardware design, since a compression unit is required in the solvent vapor recovery circuit. In addition, it retains all the disadvantages inherent in the condensation method and does not provide the ability to capture vapors of volatile solvents at low concentrations.
Thermal methods (direct combustion methods) are used to neutralize gases from easily oxidized toxic and foul-smelling impurities. The methods are based on burning flammable impurities in furnace fireboxes or torch burners. The advantage of the method is the simplicity of the equipment and versatility of use. Disadvantages: additional fuel consumption when burning low-concentrated gases, as well as the need for additional absorption or adsorption purification of gases after combustion.
It should be noted that the complex chemical composition emissions and high concentrations of toxic components predetermine multi-stage schemes cleanings that are a combination different methods.
6.5. ATMOSPHERE PROTECTION MEANS.
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. Moreover, the air
polluted by technological emissions from workshops, such as forging and pressing shops, shops for thermal and mechanical processing of metals, foundries and others, on the basis of which modern mechanical engineering is developed. In the production process of machinery and equipment, welding, mechanical processing of metals, processing of non-metallic materials, paint and varnish operations, etc. are widely used. Therefore, the atmosphere needs protection.
Atmospheric protection means must limit the presence of harmful substances in the air of the human environment at a level not exceeding the maximum permissible concentration. This is achieved by localizing harmful substances at the point of their formation, removing them from the premises or from equipment and dispersing them into the atmosphere. If the concentration of harmful substances in the atmosphere exceeds the maximum permissible concentration, then emissions are purified from harmful substances in 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 contaminated air in special devices and
its return to the production or domestic premises if the air
after cleaning in the device corresponds regulatory requirements To
supply air,
localization of toxic substances in the zone of their formation local
ventilation, purification of contaminated air in special devices,
release and dispersion into the atmosphere,
purification of process gas emissions in special devices,
release and dispersion into the atmosphere; in some cases before release
exhaust gases are diluted atmospheric air.
To comply with the maximum permissible concentrations of harmful substances in the atmospheric air of populated areas, maximum permissible emissions (MAE) of harmful substances from exhaust ventilation systems, various technological and energy installations are established.
In accordance with the requirements of GOST 17.2.02, for each designed and operating industrial enterprise, a maximum permissible limit for harmful substances into the atmosphere is established, provided that emissions of harmful substances from a given source in combination with other sources (taking into account the prospects for their development) do not create a ground concentration exceeding the maximum permissible concentration .
Devices for cleaning ventilation and process emissions into the atmosphere are divided into:
dust collectors (dry, electric filters, wet filters);
mist eliminators (low-speed and high-speed);
apparatus for collecting vapors and gases (absorption,
chemisorption, adsorption and neutralizers);
multi-stage cleaning devices (dust and gas collectors,
mists and solids traps, multi-stage
dust collectors).
Electrical cleaning (electric precipitators) is one of the most advanced types of gas purification from suspended dust and fog particles. This process is based on impact ionization of gas in the corona discharge zone, transfer of ion charge to impurity particles and deposition of the latter on the collection corona electrodes. For this purpose, electric precipitators are used.
Electrostatic precipitator circuit.
1-corona electrode
2-precipitating electrode
Aerosol particles entering the zone between the corona 1 and precipitation 2 electrodes adsorb ions on their surface, acquiring an electrical charge, and thereby receive 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 that of positive ones, electrostatic precipitators are usually made with a corona of negative polarity. The charging time of aerosol particles is short and measured in fractions of seconds. The movement of charged particles to the collecting electrode occurs under the influence of aerodynamic forces and the force of interaction between the electric field and the particle charge.
The filter is a housing 1, divided by a porous partition (filter element) 2 into two strips. Contaminated gases enter the filter and are cleaned as they pass through the filter element. Impurity particles settle on the inlet part of the porous partition and are retained 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 cleaning efficiency
filter and pressure drop across the filter element. The precipitation 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 effects.
Wet dust collectors include bubbling-foam dust collectors with failure and overflow grids.
Scheme of bubbling-foam dust collectors with failure (a) and (b)
overflow gratings.
3-lattice
In such devices, the gas for cleaning enters under the grid 3, passes through the holes in the grid and, bubbling through a layer of liquid and foam 2, is cleaned of dust by depositing particles on the inner surface of gas bubbles. The operating mode of the devices depends on the speed of air supply under the grille. At speeds up to 1 m/s, a bubbling mode of operation of the apparatus is observed. A further increase in gas velocity in the body 1 of the apparatus 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 splash removal from the apparatus. 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. The practice of operating these devices shows that they are very sensitive to uneven gas supply under the failure gratings. An uneven supply of gas leads to local blowing off of the liquid film from the grate. In addition, the grilles of the devices are prone to clogging.
To clean the air from mists of acids, alkalis, oils and other liquids, fiber filters - mist eliminators - are used. The principle of their operation is based on the deposition of droplets on the surface of the pores, followed by the flow of liquid along the fibers into the lower part of the mist eliminator. The deposition of liquid droplets occurs under the influence of Brownian diffusion or an inertial mechanism for separating pollutant particles from the gas phase on filter elements depending on the filtration speed W. 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 work successfully in an environment of dilute and concentrated acids and alkalis.
In cases where the diameters of fog droplets are 0.6...0.7 µm or less, to achieve acceptable cleaning efficiency it is necessary to increase the filtration speed to 4.5...5 m/s, which leads to noticeable spray removal from the outlet side of the filter element (splash entrainment usually occurs at speeds of 1.7...2.5 m/s), splash entrainment can be significantly reduced by using splash eliminators in the mist eliminator design. To capture liquid particles larger than 5 microns in size, splash traps made from mesh packages are used, where the capture of liquid particles occurs due to the effects of touch and inertial forces. The filtration speed in splash traps should not exceed 6 m/s.
Diagram of a high-speed mist eliminator.
1 - splash trap
3-filter element
High-speed mist eliminator with a cylindrical filter element 3, which is a perforated drum with a blind lid. 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 splash trap 1, which is a set of perforated flat and corrugated layers of vinyl plastic tapes. The splash trap and filter element are installed with the lower part into the liquid layer.
Low-velocity mist eliminator filter element diagram
3-cylinders
4-fiber filter element
5-bottom flange
6-tube water seal
In the space between 3 cylinders made of meshes,
place a fibrous filter element 4, which is secured using
flange 2 to the mist eliminator body 1. Liquid deposited on
filter element; flows onto the lower flange 5 and through the tube
water seal 6 and glass 7 are drained from the filter. Fibrous
low-velocity mist eliminators provide high
gas purification efficiency (up to 0.999) from particles smaller than 3 microns and completely captures large particles. Fibrous layers are formed from glass fiber 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 in size and provide cleaning efficiency equal to 0.9...0.98 at Ap=1500...2000 Pa, from fog with particles less than 3 microns.
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INTRODUCTION
The revival of Russian industry is the primary task of strengthening the country's economy. Without a strong, competitive industry, it is impossible to ensure the normal life of the country and people. Market relations, the independence of factories, and the departure from a planned economy dictate that manufacturers produce products that are in global demand and at minimal cost. The engineering and technical personnel of the factories 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 using modern technologies for processing parts, equipment, materials, production automation systems and product quality control. The reliability of the manufactured machines, as well as the economics of their operation, largely depend on the adopted production technology.
The urgent task is to improve the technological support for the quality of manufactured machines, and first of all their accuracy. Precision in mechanical engineering is of great importance for improving the operational quality of machines and for their production technology. Increasing the accuracy of manufacturing workpieces reduces the labor intensity of machining, and increasing the accuracy of machining reduces the labor intensity of assembly as a result of eliminating fitting work and ensuring the interchangeability of product parts.
Compared to other methods of producing machine parts, cutting provides the greatest accuracy and the greatest flexibility of the production process, creating the possibility of the fastest transition from processing workpieces of one size to processing workpieces of a different size.
The quality and durability of the tool largely determine the productivity and efficiency of the processing process, and in some cases, the general ability to obtain parts of the required shape, quality and accuracy. Improving the quality and reliability of cutting tools contributes to increasing 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 mechanical engineering industry, the range of parts produced is enormous and the variety of holes requiring processing with reamers is very large. Therefore, designers are often faced with the task of developing a new development. They can be helped in this by a package of application programs on a computer, which calculates the geometry of the cutting tool and displays the working drawing of the development on the plotter.
The design sequence and calculation methods for cutting tools are based both on the general principles 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 during design.
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 the field of tool production.
To reduce time and increase the efficiency of cutting tool design, automated computer calculations are used, the basis of which is software and mathematics.
Creating application software packages for calculating the geometric parameters of complex and particularly complex cutting tools on a computer can dramatically reduce the cost of design labor and improve the quality of cutting tool design.
Places, %; Totd - time for rest and personal needs, %; K - coefficient taking into account the type of production; Кз - coefficient taking into account assembly conditions. For the general assembly of the hydraulic lock, the standard time is: = 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. =0.06 pcs. Round to big side CP=1. ...
All known methods and means of protecting the atmosphere from chemical impurities can be combined into three groups.
The first group includes measures aimed at reducing emission power, i.e. reduction in the amount of emitted substance per unit time. The second group includes measures aimed at protecting the atmosphere by processing and neutralizing harmful emissions with special cleaning systems. The third group includes measures to regulate emissions both at individual enterprises and devices, and in the region as a whole.
To reduce the power of emissions of chemical impurities into the atmosphere, the following are most widely used:
Replacing less environmentally friendly fuels with environmentally friendly ones;
Fuel combustion using special technology;
Creation of closed production cycles.
In the first case, fuel with a lower air pollution rating is used. When burning different fuels, indicators such as ash content, the amount of sulfur dioxide and nitrogen oxides in emissions can vary greatly, therefore a total indicator of air pollution in points has been introduced, which reflects the degree of harmful effects on humans. Thus, for shale it is equal to 3.16, for Moscow region coal - 2.02, Ekibastuz coal - 1.85, Berezovsky coal - 0.50, natural gas - 0.04.
Fuel combustion using a special technology (Fig. 4.2) is carried out either in a fluidized (fluidized) bed or by preliminary gasification.
To reduce the power of sulfur emissions, solid, powdered or liquid fuels are burned in a fluidized bed, which is formed from solid particles of ash, sand or other substances (inert or reactive). Solid particles are blown into passing gases, where they swirl, mix intensively and form a forced equilibrium flow, which generally has the properties of a liquid.
Rice. 4.2. Scheme of a thermal power plant using afterburning of flue gases and injection of sorbent: 1 - steam turbine; 2 - burner; 3 - boiler; 4 - electric precipitator; 5 - generator
Coal and oil fuels undergo preliminary gasification, but in practice coal gasification is most often used. Since the produced and exhaust gases in power plants can be effectively purified, the concentrations of sulfur dioxide and particulate matter in their emissions will be minimal.
One of the promising ways to protect the atmosphere from chemical impurities is the introduction of closed production processes that minimize waste emitted into the atmosphere by reusing and consuming them, i.e., turning them into new products.
Classification of air purification systems and their parameters
Based on their state of aggregation, air pollutants are divided into dusts, mists and gaseous vapor impurities. Industrial emissions containing suspended solid or liquid particles are two-phase systems. The continuous phase in the system is gases, and the dispersed phase is solid particles or liquid droplets.
Air purification systems from dust (Fig. 4.3) are divided into four main groups: dry and wet dust collectors, as well as electrostatic precipitators and filters.
Rice. 4.3. Systems and methods for cleaning harmful emissions
When there is a high dust content in the air, dust collectors and electrostatic precipitators are used. Filters are used for fine air purification with impurity concentrations of less than 100 mg/m 3 .
To clean the air from mists (for example, acids, alkalis, oils and other liquids), filter systems called mist eliminators are used.
Means of protecting air from gas-vapor impurities depend on the chosen cleaning method. Based on the nature of the physical and chemical processes, the methods of absorption (washing emissions with solvents of impurities), chemisorption (washing emissions with solutions of reagents that chemically bind impurities), adsorption (absorption of gaseous impurities through catalysts) and thermal neutralization are distinguished. All processes for extracting suspended particles from air usually include two operations: deposition of dust particles or liquid droplets on dry or wet surfaces and removal of sediment from deposition surfaces. The main operation is sedimentation, and all dust collectors are classified according to it. However, the second operation, despite its apparent simplicity, is associated with overcoming a number of technical difficulties, which often have a decisive influence on the efficiency of cleaning or the applicability of a particular method.
The choice of one or another dust collection device, which represents a system of elements including a dust collector, an unloading unit, control equipment and a fan, is determined by the dispersed composition of the captured industrial dust particles. Since particles have a variety of shapes (balls, sticks, plates, needles, fibers, etc.), the concept of size is arbitrary for them. In the general case, it is customary to characterize the size of a particle by a value that determines the rate of its sedimentation - sedimentation diameter. It refers to the diameter of the ball, the settling speed and density of which are equal to the settling speed and density of the particles.
To purify emissions from liquid and solid impurities, various designs of collection devices are used, operating on the principle of:
Inertial sedimentation by abruptly changing the direction of the ejection velocity vector, while solid particles, under the influence of inertial forces, will tend to move in the same direction and fall into the receiving hopper;
Deposition under the influence of gravitational forces due to the different curvature of the trajectories of movement of the emission components (gases and particles), the velocity vector of which is directed horizontally;
Sedimentation under the influence of centrifugal forces by imparting a rotational movement to the discharge inside the cyclone, while solid particles are thrown back by centrifugal force to the mesh, since the centrifugal acceleration in the cyclone is up to a thousand times greater than the acceleration of gravity, this allows even very small particles to be removed from the discharge;
Mechanical filtration - filtration of emissions through a porous partition (with fibrous, granular or porous filter material), during which aerosol particles are retained, and the gas component completely passes through it.
The purification process from harmful impurities is characterized by three main parameters: overall cleaning efficiency, hydraulic resistance, and productivity. The overall cleaning efficiency shows the degree of reduction of harmful impurities in the product used and is characterized by the coefficient
where C in and C out are the concentrations of harmful impurities before and after the cleaning agent. Hydraulic resistance is defined as the difference in pressure at the inlet R input and exit R out from the cleaning system:
where ξ is the coefficient of hydraulic resistance; r and V - density (kg/m3) and air speed (m/s) in the cleaning system, respectively.
The performance of cleaning systems shows how much air passes through it per unit time (m 3 / h).
