Why is coal dust dangerous? How can you get rid of coal dust? Functioning of the asvp-lv system

E.A. Elchanov and A.I. Shor studied the consequences of snow pollution by 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 fragile, 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 even greater spread of dust occurs when frozen coal is loaded into vehicles on the surface. As a result, the area around the mine within a radius of 15-20 km is clogged with coal dust. The snow cover melts here 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, the 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 zoocenosis over an area significantly larger than the size of the aeolian dispersion of coal dust. Such a disruption of the natural cycle of matter ultimately causes very severe 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 in this case act 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 a person's lungs with such strength that it is easy to determine a person's profession by just the type of lungs. Coal dust promotes the development of coniosis. Fine quartz dust present in the air of ore mines, processing plants and some other industries leads to a person developing silicosis. [...]

The coal industry is a leader in the emission of solids and sulfur oxides into the atmosphere. However, the absolute emission of solid substances in 1996 in the coal industry amounted to 76.95 thousand tons. However, when assessing the environmental consequences of the use of coal in Russia, the work indicates “colossal emissions of coal dust and, in particular, during coal transport.” The emission of coal dust is 15 kg/tce, and the entrainment of dust 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 is 3-6 thousand tons [...]

The supply of coal dust 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 ratio Ca/8.[...]

Table 2 for the coal industry shows the specific emission of coal dust (15,000 tons) by .[...]

The pathogenic composition of dust depends on the content of free silicon dioxide in it. Coal dust with a high content in the air (about 100 g/m3) is explosive.[...]

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

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

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

The determination does not interfere with iron, aluminum, 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 car. [...]

In most cases, a mixture of coal dust and ground limestone was fed into the burners. In the furnace, when burning coal dust, limestone - calcium carbonate - dissociates into carbon dioxide and calcium oxide, and the latter, moving together with the combustion products through the flues of the boiler, interacts with sulfur and sulfur dioxide, forming calcium sulfite and calcium sulfate. Calcium sulfate and sulfite along with ash are collected in ash collectors. Free calcium oxide contained in fuel ash also binds sulfur oxides. The main disadvantage of this method of gas purification is the formation of durable 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 silt in order to determine the magnitude of excess pressure and swirl speed necessary to obtain optimal efficiency of hydrocyclones and thickening. After numerous experiments, hydrocyclones with an internal diameter of 200-300 mm were designed, when purifying with excess atmospheric pressure from waters of the sugar industry, waters contaminated with fly ash of heating plants and washing scale of hot rolling plants, the purification coefficient was 94-96%. It has been established that a hydrocyclone is not suitable for treating wastewater from the paper industry contaminated with fiber. Particular importance was attached in BNR1 to experiments aimed at developing new methods for using activated sludge for the purification of municipal or non-industrial wastewater. On larger installations working with clarified water, with a passage time of 40 minutes. the purification coefficient in terms of BODco was 91.8% and those working on the original wastewater when passing through for 1 hour - 86.3%.[...]

Polyurethane foam, coal dust, rubber crumbs, sawdust, pumice, peat, peat moss, etc. are used as adsorbents. They even use straw, which, depending on the type of oil, adsorbs it in an amount that is 8 to 30 times its weight. They use a spongy material made of polyurethane foam, which absorbs oil well and continues to float after adsorption. According to calculations, 1 m3 of polyurethane open-cell foam can sorb about 700 kg of oil from the surface of the water.[...]

4 generators will be installed at the thermal power plant. The release of a mixture of coal dust, ash and uncombustion products (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 weather vane level is 4 m/s. The mass of emissions into the atmosphere without treatment is 300 thousand tons/year.[...]

Noteworthy is the device for preparing a 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 stream of water emerging from them moves along the conical part of the funnel in a spiral manner from top to bottom, capturing pulverized coal continuously entering the funnel. A conical visor is provided above the outlet of the device to prevent coal dust from clumping in water. In order to impart rectilinear movement to the resulting coal suspension, a guide pipe is installed at the outlet of the device.[...]

Fumming is the blowing of a molten slag bath with a mixture of coal dust and air through the tuyeres of periodically operating rectangular slag distillation furnaces. Their hearth dimensions are: width up to 2.5, length up to 10 and height up to 9m. At 1250-1300°C, the oxides of lead and zinc are reduced, and the vapors of these metals sublime. Above the bath and in the flue they are oxidized by residual oxygen from the blast 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. Coal consumption is about 20% of the slag mass. The latter after fuming is dump.[...]

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

Wastewater from lignite briquette factories, obtained by wet sedimentation of coal dust, has a temperature of about 40-60 ° C, is highly turbid and dark brown in color. The deposited coal dust particles are very light (specific gravity less than or only slightly more 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.) iron sulfate grinding dust and 10% (may.) copper sulfate, add sawdust and coal dust or peat in the amount necessary to obtain a granular mass, and burn at 800-2000 °C. Thermal treatment of electroplating sludge is a passive way to solve the problem. It should be noted that burning sludge leads to air pollution and damages the environment. It is necessary to develop technologies that would allow the use of valuable chemical components of sludge and completely prevent environmental damage.[...]

In 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 at coke production plants, coal dust and soot are formed. During the coking process, a gas containing vapors of hydrocarbons (resinous substances) is released. The amount of gaseous emissions is 3-5 m3, tarry substances 0.2-0.5 kg per 1 ton of coal used.[...]

Fuses are formed as a result of enveloping a volatile solid phase (coal, shale, peat dust) with resin contained in a vapor-gas mixture during thermal processing of solid fuel in coking chambers or gas generators. When coking coal, for example, slurries are deposited during the settling of the gas phase condensate (due to the difference in their density from the density of 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 special feature of the UVV series electric precipitators is that, due to the possible occurrence of an explosion hazard when coal dust accumulates, the casings of the electrostatic precipitators are made in the form of a shaft open to the atmosphere. This prevents the case from being destroyed by “popping”. 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 covering them with beveled canopies, as well as by constructing bunker walls with large slope angles.[...]

Wastewater generated from watering lump chamotte before crushing, from washing quartzite, wet air cleaning from dust, washing scrubbers of ventilation units, cutting table during plastic molding (in old factories), washing off the floors of the coal grinding department, is contaminated only with mechanical impurities - clay, chamotte , quartzite, magnesite, chromium-magnesite and coal dust. Magnesite and chromium-nickel dust have a crystalline structure; the content of suspended substances in wastewater reaches 20-60 g/l. Fireclay dust contains a significant portion of dispersed clay particles, the concentration of suspended substances in wastewater is 15-23 g! l. Clay dust is predominantly finely dispersed; the content of suspended solids in wastewater 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 for circulation. In addition to the above, 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 fineness of the suspension pre-filtered. Effluents from laboratories are also acidic.[...]

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

Currently, another TPP-312 boiler is being reconstructed at the Ladyzhinskaya State District Power Plant according to the same scheme, using finer ground coal dust for the reburning process.[...]

Polycyclic organic compounds, the main sources of which are coal and wood stoves, coal dust when burned, and coke production, may predispose to lung cancer. They account for more than 90% of the contamination with polycyclic substances.[...]

Composition of different types of fuses,%: 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 destruction and sedimentation, as well as resinous particles formed as a result of coagulation of high-molecular multi-ring compounds. These substances are often called 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 widely - from 63% class[...]

In London, the number of fogs and their intensity increased in parallel with the growth of factories and factories. 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.[...]

A second long-term hazard to miner health that is currently of particular concern in the United States is the high levels of coal dust in the air. Conventional coal mining machines seem to 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 such dust particles is set by the federal government at 2 mg/m3. Conventional coal mining machines, not equipped with special dust collectors, produce dust concentrations of about 20 mg/m3, and often exceed the US federal government's dust limit when operating at full capacity. At the same time, during hydraulic coal mining, as measurements have shown, the dust level is only about 0.15 mg/m3, which is much lower than the established norm and, therefore, ensures greater safety for workers.[...]

Let us 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 aerusols in relation to coal dust (Lotosh. They are also inherent in other types of them. 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 environment is the pyrolysis of wood flour in a fluidized bed, in which each particle is washed on all sides by a coolant. But at the same time, it is difficult to combat the entrainment of coal dust particles and capture vapors of valuable products when they are very diluted with non-condensable gases. The amount of loss of valuable products 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 Uzbek SSR based on the use of local coals turned out to be very highly effective. The drugs in this group include the following. It has the appearance of coal dust with a faint odor of ammonia. Contains 3.6% nitrogen and 30-40% humic acids. Humophos is an ammoniated mixture of weathered Kizyl-Kaya coal and superphosphate in a 1:1 ratio. Contains 2% nitrogen, 9-10 humic acids and 10-12% plant-available phosphorus. GU-VU is a new humic fertilizer made from weathered coal in the form of initial coal dust or granules. Contains 30% humic acid. HA - humic acid, isolated from the same coals. The main active principle of carbon-humic fertilizers is humic acids.[...]

The ventilation exhaust stream freed from SBD is sent for cleaning from entrained coal dust particles into cyclones and then released into the atmosphere. The captured coal dust is returned by the auger to the adsorber.[...]

The gas containing SC>2 is treated with an absorption solution containing magnesium oxide, resulting in the formation of magnesium sulfite. After this, the absorbent containing magnesium sulfite is mixed with a carbon-containing substance. The resulting mixture is heated (200 - 400°C) in a regeneration apparatus to release 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 hydrotransport of the adsorbent, mixing of the dispersed and continuous phases is ensured by turbulent pulsations of the flow. To intensify the mixing process and accelerate the absorption of dissolved substances by active carbons, special inserts or devices 5 are often installed in pipelines, causing additional development of turbulence in the flow when the fluid speed changes in magnitude and direction. They are made in the form of cones, lattices, alternating vertical partitions of various configurations, and helical twisted elements. Waste water that has undergone purification is subjected to partial clarification from suspended coal in settling tanks or open multi-tier hydrocyclones 6. Waste coal retained in settling tanks is sent through slurry pipeline 7 for regeneration. The final release of purified water from coal dust is carried out using rapid coarse filters 8.[...]

Another variation of electrical detection involves recording selected characteristic mass lines of elements by automatically switching magnetic field strength or accelerating and focusing voltages. In this case, the ion current corresponding to each selected type of ion is integrated over a significantly longer period of time, which makes it possible to “smooth out” the instability of the ion current of the discharge source and reduce the influence of sample heterogeneity 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 sequential scanning of all mass lines. The use of selected ion detection techniques in the analysis of samples containing unknown elements is associated with significant difficulties, which is a significant drawback of this method. However, electrical detection, by reducing the time required for analysis, makes the IC method suitable for routine use, allowing studies to be carried out at relatively low resolution. Due to this, spark mass spectrometry is used to determine the elemental composition of trace contamination in coal dust aerosols and coal gasification products.

Ordinary sawdust and wood chips can be burned in boilers made for this purpose, but with coal dust it is not so simple.

Those who have already tried to heat their boiler with such fuel understood that half of it simply disappears, falling between the grate rods into the ash, while the second half is sintered into stone and prevents the burnt fuel from getting into the ash. All these reasons lead to a decrease in the quality of combustion, and therefore heat transfer.

But on the other hand, throwing away coal dust is, to say the least, stupid; it contains a large amount of energy. And here the problem can be solved by turning coal into briquettes, which we will talk about below.

More about briquetting technology

A number of parameters are used to classify fuel briquettes:

• material from which the briquette is made;
• form;
• security;
• environmental friendliness;
• type of packaging.

You can, of course, burn such dust by first heating the boiler with wood, and then pour the fine fraction on it. But this approach is not a solution; it is very troublesome, because you need to add coal dust little by little, which means often.

If you immediately put a large amount of coal dust on the firewood, it will still spill into the grate and thus, the problem of partial combustion of fuel will not go away, besides, the rest of the dust will fall between the firewood, block the flow of air and the combustion will be significantly weakened.

To circumvent all of the above inconveniences, you need to press coal dust into briquettes, which in this form will burn perfectly, releasing all their energy.

Russian developments

The solution for pressing the fine fuel fraction was invented at the beginning of the last century by Russian researcher A.P. Veshnyakov.

His idea is still used in industry and everyday life. The essence of the idea is to press wood powder into solid elements that can burn and give off heat no worse than coal itself.

Without talking about detailed technology and without listing their types, it can be noted that they come in two main types:

• using binding components, industrial combustion;
• without them, for home use.

It is important to know: briquettes made using technology that involves the use of matching elements cannot be used in everyday life. When they burn, many toxic substances are released, which are removed by special equipment during production.

We are talking about the technology of producing briquettes without the use of binding components. Production proceeds as follows:

• Initially, coal dust and small pebbles are crushed, the largest particle at the exit should not be larger than 6 mm;
• Then the mixture is dried to a moisture content of 15%. For this purpose, steam and gas type dryers are used;
• Then the dust is cooled and transferred to the press. Its effect on the fine fraction occurs with a pressure of 100 to 150 MPa, in a special stamp-type press;
• after which the finished products are sent for storage.

Requirements for particle size and compaction pressure may vary depending on the equipment used and the purpose of the fuel. For example, the UNITEK production line works with particles up to 0.25 mm and their humidity from 6 to 16%.

As a result, we obtain a product with an ash content of 15-20%, capable of withstanding a pressure of -3 kg/cm, and when dropped from a two-meter height, the loss of weight from the impact will be insignificant. The energy intensity of briquettes will depend directly on the coal dust from which they are made.

Industrial production

For the production of industrial briquettes, the following binders are used:

• oil bitumen mixture;
• cement;
• lignosulfonate additives;
• liquid glass;
• molasses.

To process small particles of coke and some other types of coal, cement and also liquid glass are often used. Such materials are used mainly in metallurgy, where the use of these substances is permitted.

Coal tar with petroleum bitumen is also used for the production of industrial coal briquettes. They cannot be used to heat residential buildings, as they release large amounts of benzopyrene and other toxic elements prohibited by the SES.

Home production

In order to make coal briquettes with your own hands, you need to have coal dust itself and clay, a safe binding element. By adding a little water, the dust and clay are mixed 10:1, so the solution acquires the desired consistency. It is very important to mix the substances thoroughly.

To create briquettes, you can use either a regular construction mixer or special equipment, such as the Weber brand. If you decide to make briquettes by hand, you can use any containers, boxes, pans, etc. as a form. At the end of production, the fuel briquettes must be dried.

Note: using equipment to create briquettes at home will be unprofitable.

Naturally, briquettes made at home are not ideal. Their strength is not as great as that of industrial analogues, they have different humidity and heat transfer.

But be that as it may, they burn perfectly in the boiler, much better than coal dust that bakes and falls through. And the cost will certainly please them. The positive reviews left about this technology speak for themselves.

How to produce coal briquettes, see the following video:

One of the main mistakes made when operating a standard coal boiler is the use of low-quality fuel. There is one single rule that must be strictly used when choosing fuel for the boiler - this is the choice of coal with exactly the characteristics specified in the technical documentation. Otherwise, the operation of the device may be not only unproductive, but also unsafe.

Fuel selection

Often, owners of heating boilers are faced with the question of using coal dust. You need to know that not every device is designed for this type of operation. First, you should study the parameters of the device, and only after that, with special responsibility, approach the choice of combustible material according to its composition, fraction, and brand.

Coal dust can differ not only in composition, but also in technical characteristics - combustion temperature, efficiency, heat transfer. Of course, all of the above data directly depends on the type of product itself. Today, the most common fuel options are the following: lignite, stone, charcoal, brown coal, anthracite. Each of them has its own parameters of humidity, ash residue, carbon content, density, and calorific value. Combustion of combustible material of different manufacturers and composition can give completely different heating results.

Kindling methods

Considering in detail the question of how to burn with coal dust, it is necessary first of all to note that a high content of its particles in the air is explosive.

There are three options for using this type of fuel.

The first and most common is the use of a special device - a burner, into which coal is supplied under pressure. In this case, combustion occurs with a continuous air flow.

The second method is to ignite the boiler in a more traditional way - with wood and coarse coal, only after this the dust is added. In this case, high concentrations of fuel elements should be avoided.

The third way to light a boiler is to produce briquettes yourself. To do this, fuel is mixed with sawdust, keeping the proportions 1/1. Add water and then mix thoroughly; the solution should resemble a plaster mixture. Small briquettes are formed from the resulting mass and dried in the open air.

Of course, the least dangerous way to burn coal dust in a boiler is to use a special device.

Not the best option. High humidity - they will burn poorly

Advantages of this type of fuel

Heating a living space using coal of various forms has a number of advantages.

Firstly, these are excellent characteristics: high heat transfer properties, long burnout time. On average, one bookmark is enough for 10-12 hours of heating.

Secondly, there is a large selection of different brands, differing in composition and density. When choosing a mixture, you should pay special attention to the moisture coefficient: the lower it is, the easier it is to use the material during operation.

As a rule, manufacturers indicate on the packaging the characteristics, as well as instructions on how to burn coal dust in various conditions - a home heating boiler, an industrial furnace, etc.

You can buy coal dust from us at a competitive price. We guarantee excellent quality and individual service to each client.

Danilov Alexander Gennadievich
Expert engineer of GorMash-YUL LLC, expert of the Unified Conformity Assessment System in the coal industry.
Co-authors: Grachev Eduard Aleksandrovich – expert of the Unified Conformity Assessment System in the coal industry;
Stanislav Vladimirovich Kulchitsky – expert of the Unified Conformity Assessment System in the coal industry;
Galiev Marat Gaptulovich – 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 mine layer being developed and the mining conditions under which an explosion is possible.

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

The degree of influence of the listed factors on the explosiveness of coal dust varies.

Influence of volatile substances.

It is generally accepted, according to research from research institutes MakNII, VostNII and others, that with an increase in volatile substances (Vcdaf), the explosiveness of coal dust increases, and there is a limit value for the release of volatiles at which the dust stops exploding. When Vcdaf ≤ 6%, the coal is not hazardous due to dust explosions; with an increase in the yield of volatiles, the frequency of occurrence of non-explosive samples decreases, and when Vcdaf ≥ 15%, the coal seam is correspondingly hazardous due to dust explosions. For coals with Vcdaf >30%, the lower explosive limit of coal dust increases slightly and practically remains constant. As an indicator of the explosiveness of coal dust, different values ​​for the yield of volatile substances are accepted in individual countries. For example, in the UK, the limiting yield of volatile substances that 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 dangerous due to dust explosions. In France, the explosiveness of coal dust for each mine layer 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”, hazardous dust explosions include coal seams with a volatile substances release of 15% or more, as well as coal seams (except anthracites) with a lower volatiles output, the explosiveness of the dust of which established by laboratory research and explosiveness testing of coal dust. This is justified by a systematic analysis of data from coal dust explosiveness tests, the results of which are shown in Fig. 1. The graph shows that at Vcdaf≤ 6%, all tested coal dust samples are non-explosive. With an increase in the yield of volatile substances, the frequency of occurrence of non-explosive samples decreases, and when Vcdaf = 15% or more, all tested coal dust samples turned out to be explosive.

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

Based on previously conducted studies, both here and abroad, we can conclude that coal dust from 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 explosiveness of coal dust. The reason is the difference in the chemical composition of volatile substances. Studies of the chemical composition of the thermal decomposition products of coal have shown that the main components of volatile substances responsible for the explosiveness of coal dust are tarry substances and unsaturated hydrocarbons on the grounds that tars begin to be released at lower temperatures, and unsaturated hydrocarbons have a low concentration explosive limit. The influence of other volatile components is of secondary importance. However, any quantitative dependence of the explosiveness of dust on the yield of these components has not been established and no explanation has been given for the fact of the explosiveness of coal dust with a yield of volatile substances of less than 10%, which practically do not contain resinous substances.

Based on ideas about the structure of coal matter, when pulverized coal particles are thermally exposed, the chains of side groups of molecules that are furthest from the central core are first 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. Considering that the process of coal dust explosion proceeds quickly, during preparation for it the particles of the dust cloud warm up to a temperature significantly lower than the temperature of the ignition source (flame front). Dust pyrolysis occurs at low temperatures, and gaseous products are characterized by a high content of methane, its homologues and unsaturated hydrocarbons. The latter makes it possible to assume that the main component of the 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 the 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%, a strict pattern is observed between the methane content in pyrolysis products and the degree of dust explosiveness, which is used for the appropriate classification of coal seams.

Presence of flammable gases in the atmosphere. So, if there is methane in the production, the lower concentration limit of explosion of coal dust is reduced and is determined by the following empirical formula: δmpv = δex exp (-0.69 СН4), (for example, with CH4 = 0%, the lower explosive limit of dust is 40 g/m3 ; at CH4=0.5% - 30 g/m3; at CH4=2% - 10 g/m3).

Influence of non-flammable substances and moisture.

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

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

The influence of the content of non-combustible substances on the explosiveness of dust from layers of different stages of metamorphism has a different effect. For coal dust with a release of volatile substances of less than 15%, the effect of the content of non-combustible components is more significant than what is the case with a higher yield of volatile substances. MakNII research has established that the explosiveness of coal dust with a release of volatile substances of less than 15% is significantly reduced when the ash content is 20-30%. In some cases, this ash content is sufficient to completely neutralize the 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 release of volatile substances is more than 30%, natural ash content does not affect the explosiveness of coal dust.

The 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 promoting the autohesion of small particles, leading to a decrease in the specific surface area of ​​dust and, consequently, to a decrease in its explosiveness. Due to its high specific heat capacity and heat of evaporation, it absorbs 4.5-5 times more heat at equal mass than inert dust. The natural moisture content in coal is insignificant and does not have a noticeable effect on the explosiveness of coal dust. But if the deposited dust is moistened to 12% or more, then it is not able to become suspended; and create explosive concentrations. At a humidity of 20-25%, dust, as a rule, does not explode.

Influence of dispersed composition of dust.

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

The influence of the dispersed composition of coal dust on its explosiveness was studied in detail at MakNII. The studies were carried out in laboratory instruments 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.

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

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

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

Based on the above, we can conclude that the explosiveness of coal dust increases with increasing dispersion, therefore, coal dust in mine workings is potentially more explosive as it moves away from the source of dust formation.

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 dust grains, we reach a point where ignition and explosion are still possible, this is called the upper explosive limit. Further increasing the distance between particles until explosion is no longer possible 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 10 g/m3.

Chemical and mineral composition of dust. Dust containing 60-70% non-flammable components 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 Rostechnadzor dated November 19, 2013 No. 550.
2. Federal norms and rules in the field of industrial safety “Instructions for combating dust in coal mines”, approved. by order of Rostechnadzor dated October 14, 2014 No. 462.
3. GOST R 54776-2011 Equipment and means for the prevention and localization of explosions of dust-air mixtures in coal mines, hazardous due to gas and dust.

Another environmental scandal related to coal - residents of the village of Vanino suffer from coal dust, which the Vanino port generously bestows on them. "Oxygen.LIFE" I read the local media and came to the conclusion that at this point on the map of the Far East there was clearly no dialogue between big business and the local population. And cutting this knot will now be quite difficult.

Rosprirodnadzor responded to mass complaints from residents of the village. Vanino (Khabarovsk Territory) “for air pollution due to coal sorting at the site of OJSC Port Vanino,” one of the largest in the Far East. Based on the results of the administrative investigation, the service banned the operation of ten crushing plants that produce harmful emissions. She also demanded that the activities of the entire enterprise be suspended for up to 90 days (there is no court decision on this yet; UPDATE - on February 3 it became known that the port was fined 250 thousand rubles for emissions).

Rosprirodnadzor received complaints from the local population throughout the past year; Vanino Sea Trade Port OJSC (one of the key shippers of Vanino Port OJSC, controlled by Mechel Group and specializing in coal exports) was brought to administrative responsibility four times for environmental violations . But nothing was done to improve. After further complaints, Rosprirodnadzor decided to check the technological installations used at the enterprise for sorting coal. And I found out that some of them were operated illegally. They were sealed on January 27. “The volume of unauthorized emissions in Rosprirodnadzor is called “significant” for the quality of atmospheric air and water area due to the “24-hour operation of the port,” writes the Kommersant newspaper.

However, last Sunday a protest rally was held in Vanino against the pollution of the air and water area of ​​Vanino Bay (Tatar Strait) with coal and alumina dust (the port specializes in processing coal and alumina). According to various media reports, from 500 to 1000 people took part in it. “Processing of cargo, including open-pit processing of coal and alumina, is carried out in violation of technology, despite the program signed last year with the government of the Khabarovsk Territory to improve environmental safety. Coal and alumina dust not only harms the health of port workers and village residents, but also represents an explosive mixture, which in another respect makes the enterprise a dangerous production facility,” says the resolution of the protesters, which was sent to the entire top leadership of the country, as well as the authorities of the Khabarovsk Territory .

Among the demands of the meeting: “immediate stop of mobile sorting, crushing plants, screens on the territory of the port of Vanino”, “immediate start of modernization of coal processing in compliance with environmental safety”, development and implementation of a regional program to improve the environment in the village, etc. However, as REGNUM reminds, “since the sale of a controlling stake in Vanino Sea Trade Port OJSC to Mechel, unrest in the Vanino region related to violations of environmental legislation has not subsided. Residents of Vanino came out to a rally for the first time in May 2013. At the same time, on behalf of the governor of the region Vyacheslav Shport An environmental program was developed and approved, but was not implemented. Another program was developed and approved by the regional government in 2016, but it was not implemented either.”

Among the demands of the rally in Vanino: “immediate stop of mobile sorting, crushing plants, screens on the territory of the port of Vanino”

It's been going on for three years now

The problem with coal dust in Vanino is long-standing, according to local media - it has been going on since 2012, when, according to environmental activists, the port began to increase the transshipment of coal to the detriment of other types of cargo (but in the interests of the new owner). Last year, Vanino residents even promised to lie down on the rails if the problem with open coal transshipment was not resolved, writes Pacific Star. “You see, even with the active intervention of the regional authorities, the port management promises a lot, but does nothing. The supervisory authorities gave the port management a whole year to correct the situation, but, alas, the port ignores all the requirements... If earlier coal was shipped from points as far as possible from the village of Vanino, now coal is literally under the windows, from crushing plants to the windows of the nearest house 150 meters at the norm is at least 500 meters,” Vadim Moskvichev, chairman of the initiative environmental group Vanino, told the media (quotes from the newspaper Pacific Star and Kommersant).

According to the eco-activist, the problem with coal dust is especially aggravated in winter: “They transport frozen coal. These machines, called crushers and seeders, work with it. They drive the coal, sift it, and in the process of passing this active dust is created. A coal curtain stands over the villages of Vanino and Toki. People are suffocating, I’m already silent about the fact that they are sick.” Moskvichev also added that as soon as the installations stopped working, the residents of Vanino immediately really felt it, there was significantly less coal dust.”

“The owners of the port, who live far from Vanino, will leave their children multi-billion dollar accounts in foreign banks. What will they leave for the children of those who live in Vanino today and who work at the port? Dust, dirt and ruined health? We do not intend to put up with this state of affairs and we, together with the residents of the Vaninsky district, will seek from the owners of the port respect for the people who live here! Elena Greshnyakova. A.i.o. head of the Vaninsky district Nikolay Ozharovsky added that the Vanino port is the only enterprise that “does not take part in the socio-economic development of the region”: “The Vanino port has not given the region a penny since the change of ownership.”

"We are doing our best"

The management of the Vanino port states that accusations against the enterprise of inaction in connection with coal dust are unfounded. “The administration of the enterprise is open to dialogue with the public and regularly posts on its website and in the media information about the implementation of the “Action Plan to Prevent Coal Dust Pollution of the Port of Vanino,” approved by the government of the Khabarovsk Territory. In 2017, the enterprise intends to increase the amount of funds allocated for the implementation of the environmental program,” the port’s press service said in a statement. And, indeed, the news feed of the Port Vanino OJSC website is more like a summary of the ongoing battle with coal dust.

“Unfortunately, coal causes dust - this is an inevitable consequence of the operation of any port complex that deals with coal. This problem is acute during periods of negative temperatures. We understand the public’s concerns, share them and will use all available methods to prevent dust,” says the General Director of Vanino Port OJSC. Valery Balakin. According to him, the company has already studied the experience of the largest coal terminals in the Baltics, Europe and Korea, which use grab transshipment technology.

And a number of measures have already been taken: “A snow machine is already operating at the port to suppress dust. We purchased four more similar installations; they will be launched in February. In conditions of negative temperatures, this is the most effective technological solution for combating coal dust. The advantage of these installations is that they produce snow that effectively deposits the dust suspension. Simplicity of design ensures reliability in operation. It is also important that this equipment will be used year-round, creating water mist in the summer.”

In addition, at the end of February the company will purchase a vacuum device that will clean access roads and storage areas at the port, which will also reduce dust levels. “The next stage is the installation of special fences in all places where we store coal,” Balakin said. The work has already begun: a number of storage areas are fenced off with reinforced concrete slabs. Slabs for fencing the remaining warehouses have been purchased and will be installed in the near future upon delivery of the necessary components.

In the second quarter of this year, the port expects the arrival of another expensive item - a high-speed vacuum loading machine designed for work in sea and river ports, or in industries where it is necessary to collect spills of dirt and debris, as well as coal, alumina, crushed stone, pulp, etc. bulk and liquid materials. The machine is a powerful industrial vacuum cleaner complete with a road sweeping attachment, and it will allow efficient and continuous cleaning of the entire production area of ​​the port.

Regarding crushers, which Rosprirodnadzor banned the use of, the port’s press service stated that “in order to reduce coal dust, the port refused to transship coal that required crushing before shipment. Crushing and screening machines are used exclusively as a magnetic separator - for the purpose of trapping metallic inclusions in incoming coal." Also, to reduce dust, the port moved coal warehouses from berths 9 and 11 to other areas of the port, distant from the residential areas of the village of Vanino.

“Unfortunately, coal causes dust - this is an inevitable consequence of the operation of any port complex that deals with coal. This problem is acute during periods of sub-zero temperatures.”

Mechel will help

Back on January 25, the Governor of the Khabarovsk Territory, Vyacheslav Shport, during a working trip, held a meeting with residents of the Vaninsky district, which was also attended by the Chairman of the Board of Directors of Mechel PJSC Igor Zyuzin. The port primarily transships coal from the Mechel company, which has long-term contracts with coal consumers in the Asia-Pacific countries, supply disruptions for which are unacceptable and could lead to loss of sales markets. Therefore, Mechel, as a client of the port, is interested in uninterrupted operation and further technological modernization of equipment and infrastructure, the General Director of Mechel-Trans Management Company LLC, a member of the board of directors of Vanino Port, said at the meeting. Alexey Lebedev.

He also added that “the company has extensive experience working with many European ports, where they have already solved the dust problem. The company, together with Port Vanino, will work on environmental measures and assist in organizing an effective dust suppression system in winter and summer.”

The governor said that a special working group would monitor the progress of the enterprise’s obligations to improve the environmental situation. “Compliance with environmental requirements is an absolute priority for us. We stand on the side of the citizens here, we will monitor the process and help them. We need healthy citizens who will help make a profit,” said Vyacheslav Shport. According to him, the group will necessarily include representatives of the public, the regional government, the district administration, deputies and port management. “Together we will form an action program to improve the environmental situation, necessarily with financial support. We will agree on the document with the Mechel company and together we will monitor its implementation. In my opinion, two weeks are enough to draft such a program,” said the head of the region.

ONF: business needs to increase its environmental responsibility

The “Vanino case” testifies not only to the difficulties of dialogue between big business and residents of a small but proud village, which, by the will of fate, became one of many remote production sites for the business giant. Moreover, as Kommersant writes, it is not critical: in case of problems with transshipment at the port of Vanino, coal from Mechel can go to other Far Eastern ports, for example, to Posyet.

But this case also showed that administrative levers for violators are weak and do not always work as they should. It is no coincidence that the special representative of the Russian President on environmental issues, ecology and transport Sergey Ivanov not so long ago he announced that fines for those enterprises that refuse to modernize their production facilities will increase several dozen times.

Experts from the Center for Public Monitoring of the All-Russian Popular Front (ONF) on environmental issues and forest protection said that the current fines for enterprises that seriously pollute the environment do not at all encourage them to take a more responsible attitude towards nature and modernize equipment. According to the Center Coordinator Vladimir Gutenev, “in the vast majority of cases, these figures do not attach significance to the damage they cause to the environment and try in every possible way to hide it, and when violations are recorded, they prefer to limit themselves to fines rather than eliminating the causes of their occurrence.”

At the same time, according to Gutenev, the topic of environmental modernization of Russian enterprises is not new at all and has been raised repeatedly over the past decade: “A significant part of enterprises not only have not carried out modernization, but also do not plan actions in this direction. At the same time, the problem of environmental pollution does not always apply to old enterprises that have been operating for decades. There are cases where newly created enterprises do not pay due attention to the environmental consequences of their activities.”

The ONF advocates strengthening control over the mandatory modernization of industries that cause environmental harm. “Perhaps, under the control of supervisory authorities, maintaining a favorable environment for the local population will become a priority production task,” Gutenev concluded.

By the way, the problem of coal dust is relevant not only for Vanino. A video has already appeared on Youtube, made in one of the schools in Nakhodka (Primorsky Territory), located near the coal terminal (probably the Vostochny port). “It’s dirty, they don’t wash them, we have to breathe it. Now I'll show you, look at the floors, okay floors, look here. Do you see this? This is what we all breathe,” the student’s voice is heard. In addition to textbooks and notebooks, students at this school bring with them a pack of napkins to wipe their desks and chairs. Each pack is enough for about a couple of days, Nakhodka television reports.

Vladimir Gutenev: “A significant part of enterprises not only have not carried out modernization, but also do not plan actions in this direction”