Owners of private houses that are heated using solid fuel boilers regularly face the same problem - coal dust accumulates in fuel storage areas. If you do not clean the room, then over time a lot of waste is collected, so many begin to wonder: is it possible and how to heat the house with coal dust. Experienced stokers say that this is quite possible. Moreover, there are two options for the use of dusty waste.

The easy way and its disadvantages

A simple way to heat a house using coal dust involves loading it into an already melted boiler. To do this, dry firewood is placed in the firebox, kindled when the combustion process reaches a certain stage, coal of a large fraction is loaded. The fuel should burn well., otherwise, after loading the dust, the fire will simply go out. If you add coal suspension at the final stage of this process, then it will smolder for a long time, while releasing a sufficient amount of heat.

What are the disadvantages of the described method? One of them has already been mentioned - if dust is loaded into the boiler untimely or in too much quantity, the combustion will stop, and when trying to re-ignite the fire, you may encounter certain difficulties. At the same time, there is no formula for the exact calculation of the required amount of dust. Here you have to focus on the internal volume of the furnace, the maximum traction force in the boiler and many other factors. That is, it is possible to determine the desired figure only by experience.

The second drawback is more serious. The fact is that coal dust itself is highly explosive. In a settled state, it does not pose a threat, but if the concentration of suspended matter in the air reaches certain values, an explosion may occur with a high degree of probability. Its destructive power will not be so great, but the main danger in such situations comes from the subsequent fire. Owners who are seriously thinking about how to heat a house with coal dust should always remember this property of crushed fuel.

Preparation of a special mixture

It was an attempt to eliminate the fire hazard arising from the use of dry coal dust that led to the emergence of a second method of heating with its help. In this case first, a special mixture is prepared, somewhat reminiscent of fuel briquettes. There is nothing complicated in this technology and, in principle, everyone can master it at home.

So, to prepare the fuel mixture, they take the same amount of coal dust and small sawdust, combine them, add water and mix until a homogeneous mass is obtained. The main secret here is to correctly determine the required amount of water, which, when added, is guided by the consistency of the mixture. It should resemble too thick plaster, be slightly damp and seize in dense lumps during mixing.

How to heat a house with coal dust, or rather a mixture based on it? To begin with, firewood is loaded into the boiler, completely filling the volume of the furnace. For this purpose it is desirable to select wood with a dense structure, which, when burned, gives good coals, and does not crumble into fine ash. After the firewood flares up, wait 10-15 minutes for a suitable temperature regime to be established in the internal volume of the boiler. Next, the burning logs are carefully leveled with a poker and the prepared mixture is spread on top of the slide.

Since the coal-sawdust mixture has a high moisture content, immediately after loading it, the temperature in the boiler will drop sharply. So it is necessary to open the full draft, and if possible, direct a strong air flow into the lower blower. To do this, you can use a regular small fan. It is turned off as soon as the combustion process is restored, and the temperature slowly rises. At the same time cover the air duct damper.

A mixture of coal dust and sawdust will not so much burn as actively smolder. This process can last up to 5 hours - it all depends on the mode of air exchange in the boiler. Experience shows that the thermal energy that is released during the complete combustion of 15 liters of the mixture is enough to heat a house with an area of ​​100-120 square meters. meters for 10-12 hours. Thus, the procedure described above will have to be repeated twice a day.

So, if you are seriously thinking about how to heat a house with coal dust, then you have two options. In the first case, you simply pour dust into the boiler, where coarse coal is already burning. At the same time, it is very important to determine the optimal amount of pulverized fuels, and also to prevent the transition of dust into a suspended state, since this is fraught with its explosion with all the consequences. The second method is more complicated - the dust is mixed with sawdust and, gradually pouring in water, the desired consistency of the mixture is achieved, which is then loaded into the boiler over burning firewood. This method requires preliminary preparation, but it is safer and more effective.

Danilov Alexander Gennadievich
Engineer-expert of "GorMash-YuL" LLC, expert of the Unified Conformity Assessment System in the coal industry.
Co-authors: Grachev Eduard Alexandrovich - expert of the Unified Conformity Assessment System in the coal industry;
Kulchitsky Stanislav Vladimirovich - expert of the Unified Conformity Assessment System in the coal industry;
Galiev Marat Gaptullovich - expert of the Unified Conformity Assessment System in the coal industry.

The explosiveness of coal dust is determined by the physical and chemical properties of the developed mine seam and the mining conditions under which an explosion is possible.

The physical and chemical properties include: the stage of coal metamorphism, quantitatively expressed by the release of volatile substances, the content of ash and moisture in coal, the dispersion of floating and deposited coal dust. The mining conditions include: the concentration of suspended and deposited coal dust in the mine working, the source of ignition, the content of methane in the atmosphere.

The degree of influence of these factors on the explosibility of coal dust is different.

Influence of volatile substances.

It is generally accepted, according to research data from research institutes MakNII, VostNII, and others, that with an increase in volatile substances (Vcdaf), the explosibility of coal dust increases, and there is a limit value for the release of volatiles, at which the dust ceases to explode. At Vcdaf ≤ 6%, the coal is not dangerous for dust explosions, with an increase in the yield of volatiles, the frequency of occurrence of non-explosive samples decreases, and at Vcdaf ≥ 15%, the coal seam is accordingly dangerous for dust explosions. For coals with Vcdaf >30%, the lower explosive limit of coal dust increases insignificantly and practically remains constant. As an indicator of the explosibility of coal dust in individual countries, different values ​​​​of the release of volatile substances have been adopted. For example, in the UK, the limiting yield of volatile substances, which determines the explosiveness of coal dust, is 20%. In Poland, the Czech Republic and Belgium, coal seams with a volatile yield of more than 12-14% are considered hazardous in terms of dust explosion. In France, the explosibility of coal dust for each mine seam is determined by laboratory tests, regardless of the release of volatile substances. In the Russian Federation, according to the current FNiP in the field of industrial safety "Safety Rules in Coal Mines", coal seams with a volatile matter yield of 15% or more, as well as coal seams (except for anthracites) with a lower volatile matter yield, the explosiveness of dust of which established by laboratory studies and tests of coal dust for explosiveness. This is justified by a systematic analysis of data from tests of coal dust for explosiveness, the results of which are shown in Fig.1. It can be seen from the graph that at Vcdaf ≤ 6%, all tested samples of coal dust are non-explosive. With an increase in the yield of volatile substances, the frequency of occurrence of non-explosive samples decreases, and at Vcdaf = 15% or more, all tested samples of coal dust turned out to be explosive.

Fig.1. Dependence of frequency n of occurrence of non-explosive coal dust on the release of volatile substances Vcdaf.

Based on previous studies, both in our country and abroad, it can be concluded that the coal dust of mine seams with a volatile matter yield of 6% or less is non-explosive according to accepted test methods. However, the release of volatile substances is not always an unambiguous indicator of the explosibility of coal dust. The reason is the difference in the chemical composition of volatile substances. Studies of the chemical composition of coal thermal decomposition products have shown that the main components of volatile substances that determine the explosiveness of coal dust are resinous substances and unsaturated hydrocarbons on the basis that resins begin to be released at lower temperatures, and unsaturated hydrocarbons have a low concentration explosive limit. The influence of other components of volatile substances is of secondary importance. However, no quantitative dependence of dust explosibility on the yield of these components has been established and no explanation has been given for the fact of explosibility of coal dust with a yield of volatile substances less than 10%, which practically do not contain resinous substances.

Based on the concept of the structure of coal matter, under thermal action on pulverized coal particles, first of all, the chains of side groups of molecules that are most distant from the central core are opened. In this case, gaseous, liquid and solid substances are formed from the products of thermal pyrolysis, synthesis, and residues of side groups. Gaseous products are a mixture of gases consisting of CO2; CO; H2; CH4; C2H6, etc. Given that the process of coal dust explosion proceeds quickly, during the preparation for it, the particles of the dust cloud are heated to a temperature much lower than the temperature of the ignition source (flame front). Dust pyrolysis occurs in a low-temperature regime, and gaseous products are characterized by a high content of methane, its homologues, and unsaturated hydrocarbons. The latter makes it possible to consider that the main component of gaseous pyrolysis products, which determines the explosiveness of coal dust, is methane (CH4). This is also confirmed by the fact that with an increase in the yield of volatile substances, the content of CH4 in pyrolysis products increases (Fig. 2.).

Fig.2. Dependence of methane content in gaseous workings of coal pyrolysis products V on the yield of volatile substances Vcdaf.

For coals with a volatile matter yield of up to 30%, there is a strict pattern between the methane content in the pyrolysis products and the degree of dust explosibility, which is used for the appropriate classification of coal seams.

The presence of combustible gases in the atmosphere. So, in the presence of methane in the production, the lower concentration explosive limit of coal dust decreases and is determined by the following empirical formula: ; at CH4=0.5% - 30 g/m3; at CH4=2% - 10 g/m3).

Influence of nonflammable substances and moisture.

Mineral non-combustible substances are constituents of coals and, according to their origin, can be divided into two groups, one of which is internal or constitutional ash, and the second is external. Constitutional ash is characterized by the fact that non-combustible substances are chemically bound with coal matter, evenly distributed in coal, and, consequently, in dust. Its content is low and usually does not exceed 2%. The content of external ash is mainly determined by the technology of coal mining. Ash as an inert additive reduces the explosibility of coal dust due to the shielding effect and the cost of heat for its heating, thereby reducing the heat balance of the system. In addition, non-combustible solids mixed with coal dust, being in the state of an aerosol, dilute the concentration of explosive particles and, at the stage of thermal pyrolysis, contribute to the termination of reaction chains. These properties of non-combustible substances led to the use of inert dust for the prevention and localization of coal dust explosions.

The material composition of non-combustible components also influences the explosive properties of coal dust. For example, if they are carbonates, then when heated to 1073K or more, a significant amount (12-15% vol.) of carbon dioxide is released from them, the admixture of which in the pyrolysis products increases the concentration limit of explosiveness of combustible gases.

The influence of the content of non-combustible substances on the explosiveness of dust in layers of different stages of metamorphism affects differently. For coal dust with a yield of volatile substances less than 15%, the influence of the content of non-combustible components is more significant than it is with a higher yield of volatile substances. MakNII research has established that the explosibility of coal dust with a volatile matter yield of less than 15% is significantly reduced at an ash content of 20-30%. In some cases, this ash content is sufficient to completely neutralize explosive dust. With an increase in the yield of volatile substances by more than 15%, the degree of influence of natural ash content decreases. When the output of volatile substances is more than 30%, the natural ash content does not affect the explosiveness of coal dust.

Moisture present in coal manifests itself in two ways. On the one hand, it acts as an inert additive, on the other hand, as a factor contributing to the autohesion of small particles, leading to a decrease in the specific surface of the dust and, consequently, to a decrease in its explosiveness. Due to the high specific heat capacity and heat of evaporation, with an equal mass, it absorbs 4.5-5 times more heat than inert dust. The content of natural moisture in coal is insignificant and does not have a noticeable effect on the explosibility of coal dust. But if the deposited dust is moistened to 12% or more, then it is not able to move into a suspended state; and create explosive concentrations. At a humidity of 20-25%, dust usually does not explode.

Influence of the disperse composition of dust.

Numerous studies have established that the degree of dispersion is an essential factor determining the explosiveness of coal dust. Particles of different sizes less than 1000 microns take part in the dust explosion, and the explosibility of coal dust increases with increasing dispersion.

The influence of the dispersed composition of coal dust on its explosibility was studied in detail at the MakNII. The studies were carried out in laboratory devices with dust from mine layers of various stages of metamorphism of the following fractions: 600-300; 300-150; 150-75; 75-50; 50-30; 30-10 and less than 10 microns, and for coal with a high yield of volatile substances (Vcdaf = 40.5%) less than 5 microns.

On fig. 3 shows the dependence of the pressure (P) developed during the explosion of coal dust on the average size of its particles (d).

As an indicator of explosiveness, the specific pressure developed during a dust explosion in a closed volume is taken. In two cases, a decrease in the explosibility index was observed for a fraction of less than 10 microns. The reason for the decrease in this indicator for fine dust is autohesion, which is more effective, the finer the dust. This was proved with the help of a small addition of coarse dust, which sharply reduces autohesion, but practically does not change the total specific surface area. As a result of this addition, a significant increase in the explosibility of dust fractions of less than 10 μm was achieved.

Noteworthy are the studies carried out in Poland. In an experimental mine, he studied the explosiveness of dusts of the same layer containing 85% of particles smaller than 75 microns in one and 96.3% of particles smaller than 15 microns in the other. For the first dust, to neutralize its explosiveness, an addition of inert dust was required, equal to 4 kg per 1 kg of coal, for the second - 6.7 kg. According to the results of this work and other studies, it was found that particles smaller than 1000 µm take part in the explosion, fine coal dust with particle sizes of 60–100 µm has the highest explosive properties, i.e. dust passing through a No. 80 sieve has the highest explosive properties of coal dust with a particle size of 45 microns.

Based on the foregoing, it can be concluded that the explosiveness of coal dust increases with increasing dispersion, therefore, coal dust in the mine workings, as it moves away from the source of dust generation, is potentially more explosive.

The amount of suspended dust. Dust suspended in the air is called dust aerosol. With a very high degree of dust, the distance between individual dust particles is very small, and the dust is non-explosive. By increasing the distance between the dust particles, we reach a point where ignition and explosion are still possible, this is called the upper explosive limit. A further increase in the distance between the particles until the explosion becomes impossible, leads to the so-called lower explosive limit. The most destructive effect is the explosion of a dust-air mixture containing 300 g of dust in 1 m3 of air. For the most dangerous coal dust, the lower explosive concentration limit is 10g/m3.

Chemical and mineral composition of dust. Dust, with the content of non-combustible components in it from 60-70%, is not explosive.

List of used literature:

1. Federal norms and rules in the field of industrial safety “Safety rules in coal mines, approved. by order of Rostekhnadzor dated November 19, 2013 No. 550.
2. Federal norms and rules in the field of industrial safety "Instructions for the fight against dust in coal mines", approved. by order of Rostekhnadzor No. 462 dated October 14, 2014.
3. GOST R 54776-2011 Equipment and means for the prevention and localization of explosions of dust-air mixtures in coal mines, dangerous for gas and dust.

Coal dust is generated during the following production operations:

• 1. Breaking coal with combines and blasting.
• 2. Hole drilling.
• 3. Loading coal by loading machines.
• 4. Transportation of coal by conveyors.
• 5. Loading at loading and unloading points.

Dust is characterized by a set of properties that determine its behavior in the air, its transformation in the body, and the effect on the body. Of the various properties of coal dust, the chemical composition, solubility, dispersion, explosiveness, shape, and electrical charge are of the greatest importance.

For the assessment of dust from the hygienic side, the most important feature is the concentration of dust in the air, its dispersion and specific gravity.

Dust concentration is the weight content of suspended dust per unit volume of air. The dust concentration is sometimes also expressed as the number of dust particles per unit volume of air, and in some foreign countries this value is taken as the main indicator of dust content. However, it is not the number of dust particles that is of paramount importance, but their mass, therefore, the weight method of hygienic assessment of air dust content was adopted as the main one. The higher the concentration of dust in the air, the greater its amount during the same period settles on the skin of workers, gets on the mucous membranes and, most importantly, enters the body through the respiratory system.

Dispersion - the degree of grinding of a substance, which determines the duration of dust in the air, penetration into the respiratory tract, sorption capacity, etc. The dispersion of dust is expressed as the percentage of individual dust fractions in relation to the total number of dust particles. For a hygienic assessment of the dispersion of dust, it is conventionally customary to divide it into the following fractions: less than 2 microns, 2-4 microns, 4-6 microns, 6-8 microns, 8-10 microns and more than 10 microns.

The dispersion of coal dust in 82 - 94% is less than 5 microns, which is an unfavorable factor, because fine dust affects the deeper parts of the respiratory tract.

The hygienic value of the specific gravity of dust is reduced mainly to the rate of its settling: the higher the specific gravity of the dust, the faster it settles and the faster the self-purification of the air occurs.

Material composition. The qualitative composition of coal dust, as a rule, is determined by the composition of the coal seam, and rock dust - by the composition of host rocks and rock layers. The quantitative ratios of the dust components depend on the technological processes and the hardness of the rocks subjected to abrasion or grinding. The content of components in the dust due to their different hardness may be different than in the massif, however, due to the complexity of sampling for analysis, their composition with an accuracy acceptable for practice is assumed to be similar to the composition of the rock.

The most important of all the ingredients of the material composition, the content of which determines the harmfulness of dust to health, is first of all free, and then bound silicon dioxide.

The shape of the particles. Coal dust consists of particles of various irregular shapes - single or collected in aggregates.

The shape of the particles can be: cube-shaped, columnar, platy, elongated-platy, lamellar, elongated-lamellar.

The predominance of one form or another depends on the physical and mechanical properties of coal (structure, fracture, hardness, brittleness, etc.). For particles larger than 40 µm, the formation microfracturing has the main influence on the shape. The shape of smaller particles is determined by the physical and mechanical properties of the coal substance.

A coal particle with a diameter of 10 microns, located at a distance of 1 m from the soil, reaches it in 4 minutes, while with a diameter of 1 micron, this time is 6.7 hours. Thus, particles with a size of 1-2 microns practically do not settle.

electrical properties. Electric charge - the presence of electric charges on the particles of the dispersed phase. Dust particles dispersed in the air carry a certain electrical charge. Their electrization occurs as a result of the adsorption of ions from the gaseous medium, the friction of particles on various surfaces or on each other. Due to the existence of many electrization conditions, a dust flow always contains particles that carry positive and negative charges. According to studies, approximately 90 out of 100 particles are charged immediately after spraying. In most cases, the average positive charge of particles of a certain size is equal to the average negative charge. The individual charge of the particles increases with their size. During the destruction of rocks, this increase obeys a quadratic law. For particles of the same size and material composition, the magnitude of the charge is determined by the dielectric properties. Particles of one sign or another may predominate in the ventilation flow. Over time, the magnitude of the charge decreases, and its predominant sign may also change. A minute after spraying, negatively charged particles predominated in the floating coal dust. After 4-5 minutes, the sign of the predominant charge of coal particles changed to the opposite.

explosive properties. Coal dust can explode. The speed of propagation of the flame of its explosion varies under the influence of many factors from several tens to hundreds of meters per second, often exceeding the sound. A powerful shock wave with a pressure of up to 1 MPa propagates ahead of the flame front.

In a dust explosion, additional energy is required to create a dust cloud of explosive concentration. Under industrial conditions, such a cloud can arise either as a result of intensive release of dust into the air during a particular technological process, or as a result of the rise of deposited dust under the influence of the energy of an ignition source.

The main factors affecting the explosiveness of dust are its dispersion and concentration, the release of volatile substances, ash content and moisture content, as well as the type of ignition source and the composition of atmospheric air.

Particles up to 1000 microns in size take part in the explosion. The explosiveness of dust increases with increasing degree of its dispersion. As the distance from the source of formation, the dust becomes more explosive, as the degree of its dispersion increases.

Factors affecting the explosiveness of coal dust:

• 1. Explosive concentration of coal dust in suspension from 16 - 96 g/m 3 to 2000 g/m 3 .
• 2. The yield of volatile substances - 15% or more.
• 3. The size of dust particles is up to 1 mm, the smaller it is, the more dangerous.

The ignition temperature of coal dust is 750 - 850 ° C. The speed of the blast wave is 1000 m / s. The strongest explosion at a concentration of 300 - 400 g/m 3 .

E.A. Elchanov and A.I. Shor studied the consequences of snow pollution with coal dust in the permafrost zone. Its increased amount near mines and quarries in the permafrost zone is due to the fact that frozen coals are more brittle, and this causes increased dust formation during their breaking. A large amount of coal dust is carried out of the mines by ventilation jets, and an even greater spread of dust occurs when frozen coal is loaded into transport on the surface. As a result, the area around the mine within a radius of 15-20 km is clogged with coal dust. The melting of the snow cover here occurs earlier than usual, and the depth of soil thawing increases by 2.5-3 times compared to the norm. All this causes the formation of lakes and increased swampiness of the territory. Due to the removal of dust, water in lakes in the spring contains up to 30-60 g/l of suspended particles and is completely unsuitable for water supply to the population. Pollution of surface waters leads to the destruction of the zoocenosis in an area that is much larger than the size of the eolian dispersion of coal dust. Such a violation of the natural circulation of matter eventually causes a very strong degradation of the landscape.[ ...]

Coal dust is partially colloidal in nature (with a negative electrical charge), especially in the presence of colloidal humic acids, which act in this case as a peptizing agent. The content of coal particles in dedusting wastewater ranges from 1 to 100 g 1 liter. Most often it is 15-20 g/l.[ ...]

Coal dust is deposited in the lungs of a person with such strength that it is easy to determine the profession of a person by one type of lung. Coal dust contributes to the development of coniosis. Finely dispersed quartz dust, present in the air of ore mines, processing plants and some other industries, leads a person to the disease of silicosis.[ ...]

The coal industry is a leader in the emission of solid substances and sulfur oxides into the atmosphere. According to the absolute emission of solid substances in 1996 in the coal industry amounted to 76.95 thousand tons. However, in the work, when assessing the environmental consequences in the process of using coal in Russia, “colossal emissions of coal dust and, in particular, during the transport of coal” are indicated. The emission of coal dust is 15 kg/tce, and dust entrainment during transport gives 3-6 kg/tce. Based on the production of 1 million tons of equivalent fuel coal, such emissions of coal dust will amount to 15 thousand tons. and dust removal during transport - 3-6 thousand tons[ ...]

The supply of pulverized coal to the boiler furnace is regulated in accordance with the required steam output. The supply of limestone is regulated taking into account the sulfur content in the fuel according to the Ca / 8 ratio.[ ...]

Table 2 for the coal industry shows the specific emission of coal dust (15000 tons) according to .[ ...]

Pathogenic compositions of dust depend on the content of free silicon dioxide in it. Coal dust at its high content in the air (about 100 g/m3) is explosive.[ ...]

In cyclone 2, coal dust is retained. It goes down into the discharge pipe, at the lower and upper ends of which there are cone gates.[ ...]

As a result of electrodeposition, coal dust, at low operating costs, is captured almost quantitatively and, without any further processing, is suitable both for briquetting and for energy purposes (combustion in specially equipped furnaces). The introduction of electrostatic precipitators had a very positive effect on the purity of water bodies in the areas of brown coal deposits.[ ...]

Explosive concentrations for coal dust are 17.2-40 g!mg for sugar dust-10.3 g!m3 for starch, sulfur, aluminum-7 g/m3.[ ...]

The third category is flammable dust, which can explode at concentrations above 65 g/m3. This includes tobacco, zinc, coal dust.[ ...]

From the cyclone, after rough cleaning from coal dust, the generator gas goes through the gas pipeline to special retort furnaces and burns in them. In the shaft of the gas generator 1 and bowl 6, from the bottom of the bowl to a level 200 mm above the grate 4, there is ash; above, for 1000 mm to the lower end of the downpipe, suspended under the loading box, there is charcoal.[ ...]

The determination does not interfere with iron, aluminium, coal dust, silicate dust containing aluminum and iron, quartz, tin and antimony.[ ...]

Coke production pollutes the air with coal dust and soot. The sources of these revenues are the following production processes: grinding coal, loading the charge into the chambers of the coke oven battery, unloading coke into the quenching wagon.[ ...]

In most cases, a mixture of coal dust and ground limestone was fed into the burners. In the combustion chamber of coal dust, limestone - calcium carbonate - dissociates into carbon dioxide and calcium oxide, and the latter, moving together with combustion products through the boiler flues, interacts with sulfuric and sulfurous anhydride, forming sulfite and calcium sulfate. Calcium sulfate and sulfite, together with ash, are captured in ash collectors. Free calcium oxide contained in fuel ash also binds sulfur oxides. The main disadvantage of this gas purification method is the formation of strong deposits of ash and calcium sulfate on heating surfaces in the temperature range of 700-1000 ° C.[ ...]

Experiments were carried out with waters contaminated with sand, coal dust, scale or lime sludge in order to determine the amount of overpressure and swirl speed required to obtain optimal hydrocyclone and thickening efficiencies. After numerous experiments, hydrocyclones with an inner diameter of 200-300 mm were designed, when cleaning with excessive atmospheric pressure from waters of the sugar industry, waters contaminated with fly ash from heating plants and washing scale of hot rolling plants, the cleaning coefficient was 94-96%. It has been established that the hydrocyclone is not suitable for the treatment of wastewater from the paper industry contaminated with fiber. Particular importance was given in WWP1 to experiments aimed at developing new methods for the use of activated sludge for the treatment of municipal or non-industrial wastewater. On enlarged plants operating with clarified water, with a passage time of 40 minutes. the purification factor in terms of BOD was 91.8% and those working on the original wastewater when passing for 1 hour - 86.3%.[ ...]

Polyurethane foam, coal dust, rubber crumb, sawdust, pumice, peat, peat moss, etc. are used as adsorbents. Even straw is used, which, depending on the type of oil, adsorbs it in an amount 8 to 30 times its mass. Spongy polyurethane foam material is used, which absorbs oil well and continues to float after being adsorbed. According to the calculated data, 1 m3 of open-cell polyurethane foam can absorb about 700 kg of oil from the water surface.[ ...]

4 generators will be installed at the TPP. Emission in a mixture of coal dust, ash and products of underburning (solid particles) of coal will be carried out through a chimney 250 m high. The average annual value of the wind speed module at the level of the weather vane is 4 m/s. The mass of emissions into the atmosphere without treatment is 300 thousand tons / year.[ ...]

Noteworthy is the device for preparing coal suspension, proposed by V. S. Besan. This device consists of a conical funnel, which is equipped with four nozzles connected to a pressure pipe. The nozzles are located in such a way that the water jet emerging from them moves spirally down the conical part of the funnel, capturing pulverized coal continuously entering the funnel. Above the outlet of the device, a conical visor is provided to prevent coal dust from clumping in the water. In order to give the resulting coal suspension a rectilinear movement, a guide pipe is installed at the outlet of the device.[ ...]

Fuming is the blowing of a molten slag bath with a mixture of coal dust and air through the tuyeres of periodically operating rectangular slag sublimation furnaces. The dimensions of their hearth: width up to 2.5, length up to 10 and height up to 9m. At 1250-1300°C lead and zinc oxides are reduced, vapors of these metals are sublimated. Above the bath and in the flue, they are oxidized by the remnants of blast oxygen and are carried away in the form of fine dust containing 15-25 and 60-75% lead and zinc, respectively. It is processed in zinc production. The consumption of coal is about 20% of the mass of the slag. The latter after fuming is dump.[ ...]

According to the studies of Soviet doctors (Chizhevsky, Sokolov), air polluted with dust, particles of coal dust and acids from factories and plants contributes to the weakening of the human body: it causes high blood pressure, drowsiness, a feeling of weakness, headaches.[ ...]

Wastewater from lignite briquette factories, being obtained by wet precipitation of coal dust, has a temperature of about 40-60 ° C, is highly turbid and dark brown in color. The precipitated particles of coal dust are very light (specific gravity less than or only slightly greater than 1.0), greasy to the touch (due to the bitumen they contain) and therefore only difficult to mix with water. Initially, coal dust particles tend to float and settle only after they have absorbed a sufficient amount of water, i.e. after several weeks or even months.[ ...]

In work, the sludge is alkalized with Ca (OH) 2 to pH = 8.5-14.0, mixed with 10-60% (may.) of iron sulfate grinding dust and 10% (may.) of copper sulfate, sawdust, coal dust are added or peat in the amount necessary to obtain a loose mass, and burned at 800-2000 ° C. Thermal treatment of galvanic production sludge is a passive way to solve the problem. Note that the burning of sludge leads to air pollution and damages the environment. It is necessary to develop such technologies that would allow the use of valuable chemical components of sludge and completely prevent environmental damage.[ ...]

On fig. 35 shows a diagram of an installation adapted by the Lurgi company for burning liquor with coal dust.[ ...]

When grinding coal, loading charge into batteries and unloading coke, coal dust and soot are formed at coke plants. During the coking process, gas is released containing vapors of hydrocarbons (resinous substances). The amount of gaseous emissions is 3-5 m3, resinous substances 0.2-0.5 kg per 1 ton of coal used.[ ...]

Fuses are formed as a result of enveloping the volatile solid phase (coal, shale, peat dust) with resin contained in the vapor-gas mixture during the thermal processing of solid fuels in coking chambers or gas generators. When coking coal, for example, fuses are deposited during the settling of the gas phase condensate (due to the difference in their density from the density of over-tar water and resin), they are periodically removed from the decanter. At low temperatures, fuses harden into a brittle material. Due to the partial dissolution of coal dust or components of pulverized shale (peat) in the resin and the physical state of the resulting materials, the separation of fuses into components is a difficult task for practical implementation.[ ...]

A feature of the UVV series electrostatic precipitators is that due to the possible occurrence of an explosion hazard during the accumulation of coal dust, the electrostatic precipitator housings are made in the form of a shaft open to the atmosphere. This prevents the destruction of the body during "pops". In addition, all internal devices of electrostatic precipitators are designed in such a way as to avoid dust accumulation. This is achieved by not including horizontal platforms or by covering them with beveled visors, as well as by arranging bunker walls with large slope angles.[ ...]

Wastewater generated from watering lump fireclay before crushing, from washing quartzite, wet cleaning of air from dust, washing scrubbers of ventilation plants, cutting table during plastic molding (at old factories), washing off the floors of the coal-grinding department, are contaminated only with mechanical impurities - clay, fireclay , quartzite, magnesite, chromium-magnesite and coal dust. Magnesite and chromium-nickel dust of a crystalline structure, the content of suspended solids in waste water reaches 20-60 g/l. Chamotte dust contains a significant part of dispersed clay particles, the concentration of suspended solids in waste water is 15-23 g!l. Clay dust is predominantly fine, the content of suspended solids in waste water is 3.5-21 g!l. The estimated content of suspended solids in the total runoff of polluted waters can be taken as 30-50 g/l. Water purified in settling tanks is used in circulation. In addition to those indicated, there are acidic waters from washing refractory powders containing hydrochloric acid up to 5 g / l and dissolved impurities - iron, beryllium, zirconium, magnesium, etc. This water is neutralized with lime and clarified in settling tanks, and beryllium water due to the fine dispersion of the suspension pre-filtered. Wastewater from laboratories is also acidic.[ ...]

Electrostatic precipitators of the UVV series (Fig. 1.102) are unified vertical lamellar dry electrostatic precipitators for capturing coal dust from gases at temperatures up to 130 °C. Just like in electrostatic precipitators of the UV series, the main elements are unified with the corresponding elements of electrostatic precipitators of the UG series. Since the coal dust is well shaken, the shaking mechanisms of the UVV electrostatic precipitators are lightweight.[ ...]

At present, Ladyzhinskaya GRES is reconstructing another TPP-312 boiler in the same way, using coal dust of finer grinding for the reburning process.[ ...]

Polycyclic organic compounds may predispose to lung cancer, the main sources of which are coal-fired and wood-burning stoves, coal dust when it is burned, and coke production. They give more than 90% pollution by polycyclic substances.[ ...]

The composition of different types of fuss,%: 30-70 substances insoluble in toluene, 20-60 resins, 2-7 ash, 3-10 water. Substances insoluble in toluene (or benzene) are coal dust of varying degrees of thermal degradation and oozing, as well as resinous particles formed as a result of coagulation of high-molecular multi-annular compounds. These substances are often referred to as free carbon. The yield of volatile substances from it is 9-17%, and from fuses - 30-65% in relation to their dry weight. The granulometric composition of the latter varies over a wide range - from 63% cells.[ ...]

In London, the amount of fogs and their intensity increased in parallel with the growth of factories and plants. 225-380 g of soot falls on 1 km 1 of London. Human lungs from coal dust lose their pink natural color and become slate-gray.[ ...]

The second long-term hazard to miner's health, which is currently of particular concern in the United States, is high levels of coal dust in the air. Conventional coal mining machines, as it were, bite into the coal seam with teeth located on a rotating drum. In this case, pieces of coal are crushed and a huge amount of fine dust is formed, which is extremely difficult to get rid of. The safe concentration of these dust particles is set by the federal government at 2 mg/m3. Conventional coal mining machines, not equipped with special dust collectors, generate dust concentrations of about 20 mg/m3, and it is not uncommon for US federal government dust levels to be exceeded when operating at full capacity. At the same time, in hydraulic coal mining, measurements have shown that the dust content is only about 0.15 mg / m3, which is much lower than the established norm and, therefore, ensures greater safety for workers.[ ...]

We also note other properties of aerosols that directly threaten health and life - their explosiveness and possible spontaneous combustion. We have already noted these properties of aerosols in relation to coal dust (Lotosh. They are also inherent in their other types. These include, for example, fine dusts of iron, aluminum, zinc. The explosion hazard and spontaneous combustion of dusts depend on their chemical composition, concentration and dispersion. [ ...]

Thus, an ideal example of wood pyrolysis in a gaseous medium is the pyrolysis of wood flour in a fluidized bed, in which each particle is washed from all sides with a heat carrier. But at the same time, it is difficult to control the entrainment of coal dust particles and to trap vapors of valuable products when they are very diluted with non-condensable gases. The value of losses of valuable products in this case may exceed their additional yields.[ ...]

In Kopeisk, Chelyabinsk region, it is planned to build a thermal power plant with a circulating fluidized bed.[ ...]

In Uzbekistan, humic preparations developed at the Institute of Chemistry of the Academy of Sciences of the UzSSR on the basis of the use of local coals turned out to be very effective. The drugs in this group include the following. It has the appearance of coal dust with a slight smell of ammonia. Contains 3.6% nitrogen and 30-40% humic acids. Humophos is an ammoniated mixture of Kizyl-Kaya weathered coal and superphosphate in a ratio of 1:1. Contains 2% nitrogen, 9-10% humic acids and 10-12% phosphorus available to plants. GU-VU is a humic fertilizer made from weathered coal in the form of initial coal dust or granules. Contains 30% humic acid. HU - humic acid, isolated from the same coals. The main active principle of coal-humic fertilizers are humic acids.[ ...]

The flow of ventilation emissions freed from SBd is sent to cyclones for cleaning from entrained particles of coal dust and then released into the atmosphere. The trapped coal dust is returned by the auger to the adsorber.[ ...]

A gas containing SC>2 is treated with an absorption solution containing magnesium oxide, whereby magnesium sulfite is formed. Thereafter, the magnesium sulfite-containing absorbent is mixed with the carbonaceous substance. The resulting mixture is heated (200 - 400°C) in a regeneration apparatus with the release of concentrated SO2 (more than 10%) for subsequent processing into sulfuric acid, and magnesium oxide is returned to the process. In order to reduce the cost of the process, coal dust or a mixture of carbon monoxide and hydrogen is used as a carbon-containing substance.[ ...]

During the hydrotransport of the adsorbent, the mixing of the dispersed and continuous phases is provided by turbulent flow pulsations. To intensify the mixing process and accelerate the absorption of dissolved substances by activated carbons, special inserts or devices 5 are often installed in pipelines, causing additional development of turbulence in the flow when the fluid velocity changes in magnitude and direction. They are made in the form of cones, lattices, alternating vertical partitions of various configurations, helically twisted elements. Waste water that has been cleaned is subjected to partial clarification from coal suspension in settling tanks or open multi-tiered hydrocyclones 6. The spent coal, retained in settling tanks, is sent to regeneration through the slurry pipeline 7. The final release of purified water from coal dust is carried out on quick coarse-grained filters 8.[ ...]

Another type of electrical detection is to register the selected characteristic mass lines of the elements by automatically switching the magnetic field strength or accelerating and focusing voltages. In this case, the ion current corresponding to each selected type of ions is integrated over a much longer time interval, which makes it possible to “smooth out” the instability of the ion current of the discharge source and reduce the effect of sample inhomogeneity on the analysis results. An increase in the registration time also causes a significant increase in the sensitivity of this detection method compared to that in the method of successive scanning of all mass lines. The application of the technique of detection of selected ions in the analysis of samples containing unknown elements is associated with significant difficulties, which is a significant disadvantage of this method. However, electrical detection, by reducing the time required for analysis, makes the IC method suitable for routine operation, allowing research at a relatively low resolution. Because of this, spark mass spectrometry is used to determine the elemental composition of trace contaminants in coal dust aerosols and coal gasification products.

How can you get rid of coal dust?

The answer - only by ceasing to mine coal - we do not consider. The experience of the Siberian Anthracite company in the Novosibirsk region shows that the problem of dust suppression can be solved using bischofite, a magnesium-based brine. This solution is poured over the road along which dump trucks loaded with coal drive.

Coal dust has become a political topic, primarily due to riots and public rallies in the port cities of the Far East. However, against suspensions in the air, which obviously do not enrich breathing, they also protest locally. For example, last year a wave of negative publications hit the Siberian Anthracite company. The leading producer and exporter of anthracite coals in Russia and in the world (UltraHighGrade) is mining in the Iskitimsky district of the Novosibirsk region.

The Novosibirsk region is not Kuzbass, although it borders on it; and it is hard to imagine that just 60 km from the metropolis of Novosibirsk, raw materials so valuable for metallurgists are mined. Residents of the village of Urgun, through which a section of the technological road passes from the mine to the processing plant, where anthracites are enriched and then loaded into wagons and sent for export, knew firsthand about the production, as they say. The village itself is located outside the sanitary protection zone, but what meets the standards on paper does not look so beautiful in real life.

However, the technological road, along which there is a constant flow of dump trucks (up to 120 trucks per day), has been running along the cut and the village for several decades. Coal woke up, crushed by wheels - and hung in the air. It should be noted that the amount of suspended solids has always been below the MPC level. But a couple of years ago, the current Urgunians got tired of it. Siberian Anthracite did not turn a blind eye to the requests of several hundred local residents and found a solution. And last year we tested it in practice.

The company modestly emphasizes that there is no particular innovation in the use of magnesium chloride brine, or bischofite. This tool has long been used in other regions, including the coal-mining Kuzbass. But for the Novosibirsk region, bischofite, of course, has become a curiosity. Chief editor "Oxygen.LIFE" Alexander Popov went to the enterprise and to Urgun to see everything not only with his own eyes, but also to breathe it in with his own lungs. It turned out that a simple innovation in general - a binder solution for dust suppression - works quite effectively, and everyone seems to be happy.

Ineffective "phlegm"

One way or another, all mining enterprises are forced to deal with dust suppression. It's just that coal miners always get more - due to the fact that coal dust is the most noticeable and unpleasant substance. Of course, this problem is most acute in ports. But even at the “Siberian Anthracite” open pits (Kolyvansky and Gorlovsky), dust accounts for about half of the total mass of pollutant emissions into the atmosphere. The problem is exacerbated during the hot period - from May to October.

For many years, yes, in fact, the entire history that the cuts have been functioning, they fought with dust in the old fashioned way - every two hours a water carrier drove along the technological road and simply poured water on it. Scientifically, this is called the "wet" method of dust suppression. As noted in a publication in the journal Production Ecology (No. 5, 2015), such methods “are used to prevent the rise into the air of dust generated during the destruction, loading and transportation of rock; for dedusting air or suppressing suspended dust with water; to prevent the re-entry of settled dust particles into the air. Water moisturizes and binds dust particles.”

Everything would be fine, but only “wet” methods of dust control are not highly effective. The main drawback is obvious even to a person who is far from coal mining: the effect of watering the road, especially in summer, will be short, like the heat in Siberia. And all this turns into huge costs for the company - after all, you need to constantly drive cars with water, which means that you need to take somewhere not only water, but also gasoline, and drivers' salaries, and bear the cost of equipment depreciation. To live "Groundhog Day" several times a day.

"Wet" methods of dealing with dust are similar to the work of Sisyphus: the effect of watering the road, especially in summer, will be short

What is bischofite?

It was necessary to find a way in which the dust settling on the road simply could not rise into the air. There are such solutions, in "Siberian Anthracite" they opted for bischofite. It is a granular or liquid magnesium chloride with a basic substance (MgCl2) content of 47%. In bischofite, which was named after the discoverer - a German geologist and scientist Gustav Bischoff- contains a large number of trace elements (about 65), due to which it surpasses sea salt and Dead Sea salt in its composition. Extraction occurs by dissolving the mineral layer with artesian water and obtaining a concentrated salt brine.

A trial purchase from a manufacturer in Volgograd and test trials of this substance took place in the Iskitimsky district at the end of last summer. But then autumn came, followed by winter, and the problem “resolved” by itself thanks to the weather. “We don't use bischofite in spring and autumn because of the rain. There is no point in winter either, in winter we are engaged in snow fighting so that cars do not get stuck and do not slip. And we use bischofite from the end of April-May and, as the experience of last year showed, somewhere until mid-October. Everything dries up, and minerals, as well as gravel and sand, thaw on the roads. We clean with graders, but it all starts to get dusty, and we have to deal with dust suppression, ”says the head of the Siberian Anthracite Motor Transport Department Alexey Fedorov.

Since this year, bischofite has been introduced into the practice of dust suppression in full. It looks like this. Concentrated particles, similar in appearance to large snow-white salt, are diluted in water in about five minutes at the rate of one to four. The brine is poured into an ordinary watering machine and sent along the technological route to the cut closest to the enterprise. First, an ordinary water carrier spills the road, and behind it - the one with the solution. Only this small, a couple of kilometers, area, which passes by Urgun, has to be sprayed. Throughout the entire length of the road, up to the Kolyvansky section (and this is more than 40 km), there is no life so close to it.

For a square meter of gravel, the quality of which would be the envy of asphalt roads in many settlements, 100 grams of crystalline magnesium chloride is enough. Then you have to wait about 15 minutes, during which a semblance of a film forms on the surface of the track. The coating has a truly unique property: it absorbs moisture from the air and retains it for a long time, from five to 10 days. The road looks as if it had just been sprinkled with rain; but coal dust does not rise and hang in the air, and, accordingly, does not scatter around. “Bishofite still has such a property that it does not dry out, but remains in a viscous state. And if a section of the road is covered with bischofite, then the cars roll it further with wheels,” adds the head of the environmental protection department of Siberian Anthracite. Artem Burtsev.

Aleksey Fedorov, Head of the Department of Motor Transport of Siberian Anthracite: “In spring and autumn we do not use bischofite because of precipitation. There is no point in winter either, in winter we are engaged in snow fighting. And we use bischofite from the end of April-May and, as shown

Are there any downsides?

Price. Siberian Anthracite does not disclose the volume of costs for the purchase of bischofite. But it is obvious that any amount somehow goes to expenses - after all, the water that was used to water the road was and remains free (it is formed when the layers are ruptured in the section itself). However, the company emphasizes that in the end they still win. First of all, no matter how much water is wasted, the “wet” method of dust suppression is a priori ineffective. And after treatment with bischofite, you can not approach the road for a week.

Bischofite also extends the life of the roadway by providing soil stabilization. And all this, as a result, has a positive effect on the service life of trucks, including engines, which suffer from coal dust no less than the lungs of Urgun residents and employees of the enterprise.

Other benefits include significant time and cost savings. As has already been said, water carts traveled along the road almost every two hours; it is enough to drive a car with a solution of bischofite once a week. The number of runs of watering machines is reduced by 264 times a month, and the total water consumption over the same period is almost 100%. Finally, according to the measurements of a specialized laboratory accredited by Rosprirodnadzor LLC Center for Hygienic Expertise, the use of bischofite reduces the presence of suspended solids in the air by 57-85%.

The main downside is the rain. “He washes everything away,” Alexey Fedorov announces the verdict. So the fact that nature does not have bad weather, the company does not agree. But at the same time, nothing remains of bischofite, no waste at all - if it is not washed away by rain, it rolls down and goes into the soil. It turns out that the land along the road in Urgun is abundantly fertilized with salts almost from the Dead Sea. By the way, bischofite is also used in Siberian Anthracite in winter. But not for irrigation, but against the freezing of coal in the cars.

And how do other companies solve the problem of coal dust?

"Oxygen.LIFE" turned with such a question to the coal miners of Kuzbass. At the cuts of the company "Southern Kuzbass" in the summer, "hydro-dedusting of technological roads" is carried out - in other words, banal watering with water, and around the clock. At sorting complexes, processing plants and transshipment points of the company, coal mass irrigation systems are installed, which moisten the coal during crushing.

In closed mining, in mines, dust becomes a factor of increased danger. But there is nowhere to get away from it: it is formed during the separation of coal and rock from the massif during the operation of combines, mining and loading machines, during blasting, as well as during loading, reloading and transportation of rock mass. The danger of coal dust, as Raspadskaya management company (part of the Evraz Group) reminds, lies in its ability to explode. “Explosiveness depends on the content of volatile substances, ash content, humidity, fineness and concentration. Coal dust is capable of exploding at a content of more than 10% of volatile substances with an ash content and a moisture content of less than 40%, with a particle size of less than 0.1 mm and at a concentration of more than 1000 mg / cubic meter. The immediate causes of coal dust explosions can be: open flames, flash or explosion of gas, blasting, malfunction of electrical networks or devices, and any exposure to high temperatures,” the company described the hazards. In addition, the high dust content of the air significantly reduces visibility, which is also dangerous for working in the mine.

To reduce the concentration of dust, modern machines are used in mines, preliminary moistening of coal seams is carried out, places of dust formation are watered, and workings are constantly ventilated. “Wetting (irrigation) of coal and rock occurs in all processes associated with the release of dust into the atmosphere: during the operation of shearers and roadheaders, drilling rigs and coal reloading along a chain of conveyors. Irrigation during the operation of the combine in the face is carried out with a special foaming agent. To eliminate local accumulations of coal dust, regular washing of mine workings and mining equipment is carried out, ”Southern Kuzbass said. They are watered not only with water, but wetting and binding substances are applied to the mine workings, and water or fogging curtains are also installed.

In addition to "hydro-dust and explosion protection", another method is used in mines - "slate mine workings". “In fact, this is an artificial increase in the ash content of coal dust that has been deposited on the surface of workings by adding inert dust made from finely ground non-combustible material, most often from dolomite, limestone or shale. High-quality inert dust should easily disperse and form a dust cloud that reduces the temperature of the flame of an explosion or flash," Raspadskaya said. This method is used as dust is deposited or "based on the forecast of the dust content of the mine air in the mine workings." According to the company, more than 200 million rubles are annually spent on dust suppression activities. Of this amount, about 40 million rubles - for the purchase of inert dust in the amount of 12 thousand tons.

The cost of fighting dust in the "Southern Kuzbass" did not disclose. But they noted that this constant work “allows to prevent the development of occupational pulmonary pathology among workers, reduce injuries and accidents during the operation of vehicles, as well as the burden on the environment. At the same time, labor productivity increases, losses during mining are reduced, and the wear and tear of mining and transport equipment is reduced.”