Methods of air pollution control
Экология и защита окружающей среды
Pollution (in the general sense) was defined in the Tenth Report of the Royal Commission on Environmental Pollution as: The introduction by man into the environment of substances or energy liable to cause hazard to human health, harm to living resources and ecological systems, damage to structure or amenity or interference with legitimate use of the environment.
МИНИСТЕРСТВО ОБРАЗОВАНИЯ РЕСПУБЛИКИ БЕЛАРУСЬ
Учреждение образования «Белорусский государственный технологический университет»
Кафедра иностранных языков
Реферат по прочитанной литературе
магистрант кафедры «Машины и аппараты химических и силикатных производств»
Дробыш Владислав Михайлович
кафедры иностранных языков
Симонова Таисия Александровна
1 Natural constituents of air 4
2 Anthropogenic emissions 5
2.1 Sulphur emissions 5
2.2 Reduction of sulphur dioxide emissions 6
2.3 Nitrogen oxides production and formation 9
2.4 Reduction of nitrogen oxide emissions 11
3 Main methods of air pollution control 13
3.1 Air pollution control by catalysts 13
3.2 Adsorption 14
3.3 Absorption 14
List of References 17
Terminological Vocabulary 18
The World Health Organisation (WHO) estimates that 500 000 people die pre-maturely each year because of exposure to ambient concentrations of airborne particulate matter. In the UK alone, this figure is around 10 000 people. World Health Organisation also estimated the annual health cost of air pollution in Austria, France and Switzerland as £30 billion, corresponding to 6% of the total mortality; about half this figure was due to vehicle pollution. In the US, the annual health cost of high particle concentrations has been estimated at £23 billion. Clearly, we are paying a high price, both in lives and money, for polluting the atmosphere.
Pollution (in the general sense) was defined in the Tenth Report of the Royal Commission on Environmental Pollution as: The introduction by man into the environment of substances or energy liable to cause hazard to human health, harm to living resources and ecological systems, damage to structure or amenity or interference with legitimate use of the environment.
This is a very broad definition, and includes many types of pollution. Note that by this definition, chemicals such as sulphur dioxide from volcanoes or methane from the decay of natural vegetation are not counted as pollution, but sulphur dioxide from coal-burning or methane from rice-growing are pollution. Radon, a radioactive gas that is a significant natural hazard in some granitic areas, is not regarded as pollution since it does not arise from peoples activities. The boundaries become more fuzzy when we are dealing with natural emissions that are influenced by our actions for example, there are completely natural biogenic emissions of terpenes from forests, and our activities in changing the local patterns of land use have an indirect effect on these emissions. Pollution from our activities is called anthropogenic, while that from animals or plants is said to be biogenic. Originally, air pollution was taken to include only substances from which environmental damage was anticipated because of their toxicity or their specific capacity to damage organisms or structures.
People tend to refer to air as though it consists of air molecules, which is evidence of the spatial and temporal constancy of its properties that we take for granted. Consider first the molecular components that make up unpolluted air. Air consists of a number of gases that have fairly constant average proportions, both at different horizontal and vertical positions and at different times. Table 1 gives the proportions of the gases that are present at concentrations of around and above 1 ppm.
Table 1 Proportions of molecules in clear dry air
Proportion by volume
The average molar mass of dry air can be found by summing the products of the proportions by volume and molar masses of its major components.
Mixed into the quite uniform population of atmospheric molecules is a large range of additional materials that vary greatly in concentration both in space and time:
All fossil fuels contain sulphur, most of which is released as sulphur dioxide during combustion. Almost all the anthropogenic sulphur contribution is due to fossil fuel combustion. Different fuels offer a wide range of sulphur contents:
The major natural sulphur emissions are in the reduced forms of H2S (hydrogen sulphide), CS2 (carbon disulphide) or COS (carbonyl sulphide), and the organic forms CH3SH (methyl mercaptan), CH3SCH3 (dimethyl sulphide, or DMS) and CH3SSCH3 (dimethyl disulphide, or DMDS). Dimethyl sulphide is produced by marine phytoplankton and oxidised to SO2 in the atmosphere; H2S from decay processes in soil and vegetation; and SO2 from volcanoes. Whatever their original form, much of these sulphur compounds eventually get oxidised to gaseous SO2 or to sulphate aerosol. The natural sources are now heavily outweighed by human ones, principally fossil fuel combustion. Since 90% of the biogenic emission is as DMS, and an even higher proportion of the human emission is as SO2, we have a clear demarcation between the source types. Since most of the DMS comes from oceans in the southern hemisphere, and most of the human SO2 from fossil fuel emissions in the northern hemisphere, we also have a geographical split.
About 66% of UK emissions are currently from power stations, and are emitted from chimneys several hundred metres above ground level. For example, a typical 2000 MW power station as operated by National Power or PowerGen burns up to 10 000 tonnes of coal per day, producing between 500 and 1000 tonnes of SO2 per day. The total UK generating capacity of about 60 000 MW is responsible for the emission of about 1 Mt of sulphur dioxide per year.
Emissions are not usually spread uniformly across the country. In the UK the National Atmospheric Emissions Inventory (NAEI) compiles very detailed maps of estimated emissions on a 10 × 10 km grid. These estimates are updated annually. Two factors drive SO2 emissions population and power stations. There are clusters of emissions around the large urban centres, because these areas are industrial as well as population centres. There are also clusters around the group of coal-fired power stations in the English East Midlands. Areas of low population density, such as the Highlands of Scotland and central Wales, have correspondingly low emission densities.
Emissions from the power station sector were almost constant until the early 1990s, and then fell steadily under the combined influence of desulphurisation and the switch to gas from coal. Industrial and domestic emissions fell throughout the period. This decline conceals a major redistribution of source types the power stations have been moved out of the urban areas into greenfield rural sites near the coalfields, while domestic coal combustion for space heating has been almost completely replaced by gas central heating.
Burn less fuel! It is self-evident that, other things being equal, we can always reduce pollutant emissions by burning less fuel. However, for several hundred years, as we have already seen, the rising standards of living of the developed countries have been based fundamentally on production and consumption of energy that has mostly been derived from fossil fuel. We live in an increasingly energy-intensive society, and reductions to our quality of life in order to save energy are not yet politically acceptable. Many measures, such as improved thermal insulation and draught proofing of buildings, offer enormous potential for improved quality of life and reduction of emissions. Wonderful opportunities for change have been missed. Other attractive options, such as combined heat and power, that can raise the overall energy efficiency of fossil fuel combustion from below 40% to above 80%, have also been largely ignored. Some countries have made more progress than others in Copenhagen, for example, new houses are automatically supplied with hot water from the district heating scheme.
Fuel substitution. This involves the use of a lower-S fuel to reduce emissions, and is very logical, but may have other implications. In the UK, a large investment in coal-fired stations was made in the 1960s, with coal sourced from the nationalised British coal pits. Most British coal, particularly in the Trent valley where the power stations are concentrated, is not low-sulphur. When acid deposition and the sulphur content of coal became an issue in the 1970s, there was little flexibility for these stations to import low-sulphur coal. In the 1980s and 1990s, the British coal industry collapsed under both economic and political pressures, increasing the freedom of power stations to import low-sulphur coal. In addition, the privatised electricity generators are now free to construct gasfired power stations that emit much less sulphur dioxide.
Fuel cleaning. The coal used in large-scale generating plant is ground in a ball mill to the texture of a fine powder so that it can be blown down pipes and mixed with air before combustion. Since the sulphur-containing pyrites occur as physically-distinct particles having a different density to the coal, a process such as froth flotation can be used to separate the relatively dense flakes of pyrites from the powdered coal. Reductions of 80% in S content can be achieved, but 40% is more typical and this process is not widely used.
Flue Gas Desulphurisation (FGD). Chemical engineering plant can be built into or added onto power stations to remove most of the sulphur dioxide from the combustion (flue) gases before they are exhausted to atmosphere. Several different methods are available. In the most popular, a finely divided limestone slurry is sprayed into the flue gas (Figure 1). The calcium carbonate from the lime-stone reacts with the SO2 to produce hydrated calcium sulphate (gypsum), which can be used to make plasterboard for the building industry.
Figure 1 Calcium carbonate FGD system.
In a modification of the above, a lime slurry is atomised by a spinning disc. Although, the reaction between the absorbent and the acid gas takes place mainly in the aqueous phase, the water content and rate of evaporation are controlled to give dry calcium sulphite which is captured in a conventional dust collector and can be used for landfill or cement manufacture.
Finally, for plants located near the sea, the natural alkalinity of sea water can be utilised to form sulphuric acid in a packed bed absorber.
The acid effluent is normally disposed of at sea, which may or may not be environmentally acceptable. This process is a good example of the need to consider air, water and land pollution as a whole when evaluating different control strategies.
Although sulphur emissions are greatly reduced, other issues are raised. Limestone must be quarried in, and transported from, rural areas, and the gypsum may have to be disposed of to landfill if a market cannot be found for it. There is then a consequent risk of leachate creating a water pollution problem. The UK electricity providers have installed FGD systems on the minimum number of power stations necessary in order to meet European Union targets on sulphur emission reduction. West Germany, in contrast, installed FGD on 40 000 MW of capacity between 1982 and 1991, which reduced annual SO2 emissions from 1.6 Mt to 0.2 Mt. In 1990, with the unification of East and West Germany, emissions rose sharply because the East Germans had been burning 300 Mt/a of high-sulphur soft brown coal. There is currently a second wave of FGD retrofits being made to existing power stations which is expected to bring total German emissions down from 6 Mt to 0.6 Mt by 2005.
Although the old industrialised countries have the wealth and level of technology to lower SO2 emissions to whatever value they choose, we cannot be complacent on a global basis. For example, China currently burns around 1000 Mt coal and emits 15 Mt SO2. By 2020, around 2000 Mt coal will be burnet, emitting up to 55 Mt SO2 depending on the sulphur content of the coal and the level of sulphur emission control installed on new plants.
The two principal oxides of nitrogen are nitric oxide (NO) and nitrogen dioxide (NO2). The sum of these two is known as NOx (pronounced either as en-oh-ex or as knocks). Despite their quite different physical properties, chemical affinities and environmental impacts, they are often lumped together. Combustion always produces a mixture of NO2 and NO, although typically more than 90% of combustion NOx production is in the form of NO.
Nitric oxide is formed in two distinct ways:
the air. The reactions can be summarised by the Zeldovitch mechanism:
This is highly endothermic, so that thermal NO production is at a maximum in the highest-temperature regions of a combustion chamber.
Fuel NO is formed from nitrogen in the fuel. Typically, fuel nitrogen contents are 0.51.5% in oil and coal, and rather less in gas.
Nitric oxide is also emitted from soils, but it has proved harder to quantify the source strength. Nitrifying bacteria produce both nitric and nitrous oxide anaerobic production of NO is thought to dominate overall.
The annual total is less than for sulphur dioxide, with a different balance between source types. Power stations make up only a fifth; while road transport, which contributed only a tiny proportion of the SO2 emissions, contributes nearly half of the N emissions. The similarity of the road transport emissions in 1970 and 1998 conceals a large rise to a peak of 400 ktonnes in 1990 before they were controlled by catalytic converters. The emissions are in fact quite evenly distributed among coal, petrol and diesel fuels. This balance naturally affects the priority areas for control measures. It is important to note that, despite the precision with which the emissions are quoted, the error on these figures (and on those of corresponding emissions of other gases) has been estimated to be 1520%. The total weight of nitrogen emitted is some 500 kt, equivalent to more than half the total nitrogen used in UK fertiliser. Hence it should be anticipated that the nitrogen, once returned to the surface, will have a significant impact on both managed and natural ecosystems.
Although most of the direct emission will be as NO, the source strengths are given as NO2 equivalent since all the NO is potentially available for oxidation to NO2. Within this global total of about 150 Mt, European emissions account for about 20 Mt. Some 70% of the total release is due to human activities or to put it another way, we are emitting more than twice as much as the whole Planet. An indication of the uncertainty in compiling these estimates is that the global total is predicted to lie in the range 60300 Mt. As with SO2 and ammonia, there are large variations in emission density with location by a factor of at least 30 between the heavily populated regions of the Netherlands, Germany and the UK on the one hand, and sparsely inhabited regions such as Scandinavia and northern Scotland on the other.
Only a small proportion of the NO2 found in the atmosphere was released in that form from sources. The remainder has been created in the atmosphere as part of the same photochemical activity that is responsible for ozone formation. The nitric oxide from fossil fuel combustion reacts with ozone
During daylight, the NO2 absorbs blue and UV radiation <420 nm and decomposes back to NO and O3, resulting in a photochemical equilibrium between the four gases. In rural areas, away from the NO sources, the NO2 concentration is usually considerably higher than that of NO. In urban areas, the O3 becomes depleted and the balance moves in favour of NO. The production of ozone, which requires more complex cycles involving organic compounds and radicals.
The principal sink for NO x is oxidation to nitric acid HNO3.
In the daytime:
and at night:
The resulting lifetime of NOx is only about a day. Furthermore, HNO3 is highly soluble in water and easily removed by precipitation, so it has not been clear what acts as the effective NOx reservoir which is required to explain its occurrence in regions remote from anthropogenic sources. The likely route is thought to be via peroxyacetyl nitrate (CH3C(O)OONO2, usually referred to as PAN). Peroxyacetyl nitrate is produced in the troposphere by photochemical oxidation of carbonyl compounds in the presence of NOx. For example, from acetaldehyde CH3CHO
Since PAN is only slightly soluble in water, it is not removed effectively by precipitation processes. The main loss route is by thermal decomposition which regenerates NOx:
This decomposition process has a time constant of 1 h at 295 K but several months at 250 K. Hence it is thought that PAN generated close to NOx sources moves into the upper troposphere and lower stratosphere, where the low temperatures allow it to be transported long distances before releasing NOx. This process maintains NOx concentrations at 50100 ppt throughout the remote troposphere.
Burn less fuel! Fewer motor cars, smaller engines, more public transport, more home insulation and similar measures . Since the same combustion processes are involved, all the arguments and methods that applied to SO2 will reduce NOx production correspondingly.
Low-nitrogen fuel. There is not much to be gained by using low-N coal or oil, since they tend to have similar N content. Also, a perversity of thermodynamics means that low-N fuels convert their N more efficiently to NO than do high-N fuels, offsetting the expected benefit.
Peak temperature reduction. The endothermic nature of thermal NO generation means that production can be lessened by reducing peak temperatures everywhere within the combustion zone; it is better to have a uniform distribution at the average temperature than to have high-temperature peaks and low-temperature troughs. A technique called Flue Gas Recirculation can also be used, in which a small proportion of the flue gases (which are inert because their oxygen has been used up) are fed back to dilute the airfuel mixture before combustion and reduce the intensity of the flame.
Airfuel ratio. Fuel NO can be reduced by making the combustion fuel-rich (i.e. by reducing the airfuel ratio). However, this also reduces the thermal efficiency, which is of paramount importance to large-scale users such as electricity generators, and means that more fuel has to be burnt. Hence it is not widely used. Low-NO x burners. Use burner aerodynamics and combustion chamber design to slow the rate at which fuel and air are mixed and burnt, giving long lazy flames and the minimum number of hot-spots. N is still released from the fuel, but under reducing conditions so that it forms N2 rather than NO. These burners can be retrofitted to existing plant, and have the potential to reduce fuel-NO by 40%. The EC Large Combustion Plant Directive specifies emission limits for new plant. The national total emission from existing plant that has a capacity greater than 50 MW (thermal) also has to be reduced by 15% (1993) and 30% (1998) from 1980 values. In order to meet these targets in the UK, twelve of the coal-fired power stations in England and Wales, representing more than 70% of total coal-fired capacity, have been retrofitted with low-NOx burners.
Flue Gas Denitrification. Conventional coal and oil-fired power stations may be used in areas with tight NOx emission limits. Also, nitrogen-rich fuels such as sewage, refuse, some heating oils and waste wood can generate high NOx emissions. For such emissions, two types of flue gas denitrification (deNOx) system are in use. The first, used at lower nitrogen loads, operates without a catalyst at temperatures of 8501000 °C. Ammonia or urea is injected into the flue gas at the combustion chamber outlet. The second again involves the injection of ammonia or urea, but this time at lower temperatures (250350 °C) in the presence of a catalyst such as vanadium pentoxide or titanium dioxide.
This process is expensive; it has been fitted to about 150 plants in Germany, the US and Japan, but is not used in the UK. There may be up to 5 ppm of ammonia slip, which can in turn be controlled with transition metal ions in the catalyst washcoat. The selective catalytic converter is upstream of any dust removal equipment, so the operating conditions for such a catalyst are poor, with very high dust loadings and acid gas concentrations, and the pore structure can get blocked with sulphates and fly ash. Partial regeneration may be possible by soot blowing.
The 1999 CLRTAP Gothenburg Protocol caps EU15 NOx emissions in 2010 at 6.65 Mt (2.02 Mt as N). EU15 countries have not been as successful in reducing their N emissions as they have been for S. This reflects the fewer opportunities for reducing N emissions via low N fuel, fuel substitution and flue gas deNox.
A catalyst is a material that increases the rate of a chemical reaction by lowering the activation energy for a particular step in the reaction sequence; the catalyst does not itself get changed in the reaction. The reaction products can be controlled by choice of catalyst for example, platinum will catalyse the full oxidation of ethylene to carbon dioxide and water, whereas vanadium catalyses partial oxidation to aldehyde. Catalytic control of air pollutants has been given a huge role in the reduction of motor vehicle emissions; there are also many industrial process emissions that can be reduced by catalytic conversion. The effectiveness of catalytic reactions partially depends on access by the reactants to the catalytic sites. Hence catalysts are usually presented as a coating on a porous support matrix having large surface area. Common matrix materials, such as Al2O3, SiO2 and TiO2, are applied as a washcoat to an inert mechanical substrate. This washcoat is precipitated from solution and then heat treated to form a network of 25 µm particles interlaced with pores 110 µm across. Such a washcoat can have a surface area as high as 200 m2/g. Choice of washcoat may be critical for particular gases for example, alumina reacts with sulphur dioxide and is unsuitable for catalysing sulphurous exhaust gases. The washcoat is then impregnated with the catalyst by soaking it in a solution containing a salt such as Pt(NH3)+2. The exhaust gases to be treated could be passed directly through the catalysed washcoat. However, at high flow rates this generates high pressure drops and hence energy costs (or equivalently, a loss of power). To reduce the pressure drop, the washcoat is applied to an inert ceramic monolith having a honeycomb structure of 5060 channels cm2, each channel being 12 mm across and giving a surface area density of 0.3 m2/g. Temperature is another important factor. Catalysis of relatively cold gases will be limited by the chemical reaction rates at the catalyst sites, while for hot gases the rate-limiting process will be diffusion of reactant and product molecules to and from the sites.
An interesting application of catalytic control is for ozone in the cabins of high-altitude jets. The WHO guideline for personal exposure to ozone is 0.1 ppm. During very high pollution episodes in Los Angeles the concentration has risen to 0.6 ppm. Yet long haul passenger aircraft routinely fly at altitudes at which the ozone concentration is several ppm. Although this air is very thin, if it is com-pressed for use as the source air for cabin air conditioning the ozone content could be unacceptably high. Ozone abaters based on a palladium catalyst are carried aboard such aircraft.
Gaseous air pollutants such as organics are captured on the surface of a bed of porous material (the adsorbent) through which the gas flows. The adsorbents used are materials such as activated carbon (charcoal made from wood or coconut shells), silica gel (sodium silicate), alumina, synthetic zeolites and clays such as fullers earth (magnesium aluminium silicates). Activation refers to the thermal pretreatment of the adsorbent so as to maximise its surface area per unit volume. This large specific surface area is an essential requirement for good adsorption systems. Commonly-used adsorbers such as silica gel and activated charcoal have surface areas of up to 2 km2 per kg, and adsorption capacities of up to 0.5 kg/kg. The adsorption process may be physical, (due primarily to Van der Waals short-range forces), or it may be chemical. When it has become saturated, the adsorbent is regenerated by heating (often with steam) with or without a reduction in pressure. Adsorption is most effective at high concentration and low temperature. The relationship between the concentrations in the gas and solid phases at a particular temperature is known as the adsorption isotherm. In general, the concentration in the solid phase increases with molecular weight and pollutant concentration and decreases with increasing temperature. The adsorption is most effective for non-polar (hydrophobic) compounds such as hydrocarbons, and less so for polar (hydrophylic) compounds such as organic acids and alcohols.
The gas stream is given intimate contact with an absorbing solution by means of bubbling or spraying. The absorption may either be chemical (by reaction) or physical (by dissolution). Solvents in common use include water, mineral oils and aqueous solutions. Gases that are commonly controlled by absorption include HCl, H2SO4, HCN, H2S, NH3, Cl2 and organic vapours such as formaldehyde, ethylene and benzene. The absorption process depends on the equilibrium curve between the gas and liquid phases and on the mass transfer between the two, which in turn is a function of the driving force divided by the resistance.
In commercial absorbers, the gas and solvent are brought into intimate contact, with equilibrium being achieved if the results are to be predictable, before the cleaned gas and solvent are separated. In stagewise absorption, such as tray scrubbers, the gas is bubbled through the liquid to achieve one absorption step under one set of equilibrium conditions before going on to the next step. A vertical casing contains several trays one above the other.
Solvent cascades from the top downwards, while gas moves upwards (counter-current absorption). Each tray has many small vents across its surface through which the gas bubbles, into and through the layer of solvent. These bubbles provide the high surface area and thin gassolvent interface necessary for efficient movement of the gas into the solvent. In continuous differential contact systems, such as packed towers, the interfacial surface is maintained on a subdivided solid packing (Figure 2). Very high efficiencies, greater than 99.9%, can be achieved.
Figure 2 A packed absorption tower.
A common application of gas scrubbers is for odour control. Some gases have extremely low odour thresholds, which are unrelated to their toxicity, and scrubbers must operate at consistently high efficiencies to avoid odour complaints. Often, the odorous contaminant is absorbed into a solvent, then reacted with an oxidizing agent such as potassium permanganate to fix it as a less harmful compound.
The three major groups of gaseous air pollutants by historical importance, concentration, and overall effects on plants and animals (including people), are sulphur dioxide (SO2), oxides of nitrogen (NOx = NONO2) and ozone (O3). Sulphur dioxide and nitric oxide (NO) are primary pollutants they are emitted directly from sources. We have looked at the main sources of these and other primary gases, and have also considered some of the methods of control that can be used to reduce emissions and their concentrations when required. Nitrogen dioxide (NO2) is both primary and secondary some is emitted by combustion processes, while some is formed in the atmosphere during chemical reactions. Production of SO2 is commonly associated with that of black smoke, because it was the co-production of these two materials during fossil fuel combustion that was responsible for severe pollution episodes such as the London smogs of the 1950s and 1960s.
1. Air pollution / Jeremy Colls 2nd ed. Published by Spon Press, London, 2002 17-113 pp. (111300)
Absorbe впитывать; поглощать; воспринимать.
~ force сила сцепления.
Adsorb поглощение, адсорбирование.
Alkoxy radical алкоксирадикал.
Altitude высота над уровнем моря.
Ammonia аммиак, нашатырный спирт.
Aperture отверстие, диафрагма.
Arbitrarily произвольный; взятый из головы.
Belt приводной ремень.
Biodegradable биологически разложимый.
Blast порыв; взрыв.
at full ~ на полную мощность.
~ off взлетать, взмывать.
~er паровой котёл.
Bulk насыпной/навальный груз.
Burden груз, нагрузка.
Cap колпачёк, крышка.
Carboniferous угленосный, каменноугольный.
Ceiling [si:liη] поток.
Charcoal древесный уголь.
Chimney дымовая труба.
Combustion сгорание, горение.
Computation вычисление, расчёт.
Conceal укрывать, скрывать.
Contaminant загрязняющее вещество.
Crude сырой, грубый.
Current струя, поток.
Curve кривая линия, изгиб.
~ed line пунктирная линия.
Decelerate замедлять скорость.
Depart отклоняться от.
Deplete истощать, исчерпывать.
Deposition отложение, осадок.
Depression область низкого давления; впадина.
Dilute разбавлять, ослаблять.
Displacement замещение, вытеснение.
Dispersion дисперсия, разброс.
Distillation дестиляция, перегонка, ректификация; возгонка.
Dolomite доломит; горький шпат.
Drag лобовое сопротивление.
~ force сила сопротивления.
Dye краситель; краска.
Effluent жидкие отходы.
Emit испускать, излучать.
Emission выделение; излучение.
Enhance улучшать, повышать.
Epoxy эпоксидная смола.
Erode размывать; разъедать.
Evaporate испаряться; пропадать.
Exhaust выхлопная труба, выхлопные газы.
Fan heater нагревательный вентилятор.
Feedback обратная связь.
Feedstock промышленное сырьё.
Fertiliser удобрение, минеральное удобрение.
Flexibility гибкость, податливость.
Flotation флотация, флотационное обогащение.
Flow течение, поток.
~ oil мазут.
Grassland сельскохозяйственные угодья.
Graticule сетка коардинат.
Greenhouse gas парниковые газы.
Grid координатная сетка.
Honeycomb шестиугольный мозаичный узор.
Hot-spot горячая точка.
Impermeable непроницаемый, герметический.
Incenerator мусоросжигательная печь.
Inlet впускное/входное отверстие.
Lapse rate градиент.
Lead свинец; графит.
Lignite бурый уголь.
Loess лесс (известковая горная осадочная порода)
Lump ком, кусок.
Magnitude величина, масштаб.
Manner способ, метод.
Mean free path длинна свободного пробега.
Minority быть в меньшинстве.
~ force равнодействующая сила.
Nitrify нитрифицировать, превращать в силитру.
Notation система обозначения.
Obstruct помеха, запор.
Outlet выходное отверстие.
Output выходные данные.
Overlap частично совпадать.
Paraffin oil керосин.
Pattern конфигурация, расположение.
Penetrates проникать в/на.
Permanganate соль марганцовой кислоты.
Peroxy перекислый радикал.
Pit скважина, шахта, колодец.
Plasterboard гипсовые щиты.
Plume плюмаж; струя.
Pollutant загрязняющий агент.
Precipitate осаждать, выпадать в осадок.
Preheat предварительный подогрев.
Propellant метательное взрывчатое вещество.
Pyrolysis пиролиз, высокотемпературное разложение до мономеров.
Quarry каменоломня; карьер.
Ramp скат, уклон.
Refuse мусор, отходы, отбросы.
Residue остаток, осадок.
Rubbish мусор, отбросы, хлам.
Saltation скачок, прыжок, неожиданное изменение движения.
Sample образец, проба.
Sewage сточные воды.
Shear [ʃiə r] стричь; остричь.
~ off надламывать.
~ stress напряжение сдвига.
Silica кремнезём, кварц, двуокись кремния, кварцевый ангидрид.
Sink слив, сток.
Sinter шлак, окалина.
Slip скользить, сползать.
~ correction коррекция скольжения.
Slurry пульпа, жидкое цементное тесто, жидкая глина.
Soup повышать мощность; густой туман; нитроглицерин.
Streamline придавать обтекаемую форму.
Submultiples целыми частями.
~ic acid серная кислота.
Sundry разного рода.
Tank бак, цистерна.
~ speed конечная скорость.
Throughput пропускная способность, производительность.
Tin олово; белая жесть.
Trough жёлоб; впадина.
Twig ветка, ответвление.
Updraft восходящий поток.
Urea мочевина, карбамид.
Uric acid мочевая кислота.
Vent вентиляционное отверстие.
Washcoat омываемое покрытие.
Реферат состоит из введения, трёх глав и заключения, в которых рассмотрены основные компоненты воздуха, основные антропогенные выбросы и основные методы снижения их концентрации. В первом разделе реферата приводятся основные вещества, находящиеся в воздухе, и их процентное отношение. В следующем разделе приводится обзор основных источников антропогенного загрязнения воздуха оксидами азота и диоксидом серы, также основные методы по снижению этих выбросов. В третьем разделе рассматриваются некоторые из основных методов очистки воздуха. На предприятиях производства строительных материалов выбросы, указанных выше загрязняющих агентов, часто превышают установленные нормы на выбросы. Поэтому установки для очистки газов нужны для сохранения атмосферного воздуха в пригодном для дыхания и жизни виде.
The abstract consists of an introduction, three chapters and conclusion, in which major air compounds, main anthropogenic emissions and essential methods of concentration declining are discussed. The first section describes basic substances in the air, and their percentage. The following section provides an overview of the main sources of anthropogenic air pollution by nitrogen oxides and sulfur dioxide, also the main methods of these emissions reduction. The third section discusses some of the basic methods of air purification. At the enterprises producing building materials emissions of the mentioned above pollutants often exceed the required standards for emissions. Therefore, plants for gas purification are needed to save the atmospheric air in proper form for breathing and life.
Рэферат складаецца з уводзiн, трох частак i заключэння, у якiх разгледжаны асноуныя кампаненты паветра, асноўныя антрапагенныя выкіды і асноўныя метады зніжэння іх канцэнтрацыі. У першым раздзеле рэферата прыводзяцца асноуныя рэчывы, якія знаходзяцца ў паветры, і іх працэнтнае стаўленне. У наступным раздзеле прыводзіцца агляд асноуных крыніц антрапагеннага забруджвання паветра аксідамі азота і дыаксідам серы. Таксама ў гэтым раздзеле прыводзяцца асноўныя метады па зніжэнню гэтых выкідаў. У трэйцім раздзеле разглядаюцца некаторыя з асноўных метадаў ачысткі паветра. На прадпрыемствах вытворчасці будаўнічых матэрыялаў выкіды указыных вышэй забруджваючых агентаў часта перавышаюць устаноўленныя нормы на выкіды. Таму ўстаноўкі для ачысткі газаў патрэбны для захавання атмасфернага паветра у прыдатным для дыхання і жыцця выглядзе.
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