home

What substances are obtained from methane. Physicochemical properties of methane

Natural gas is gaseous hydrocarbons formed in the bowels of the earth. It is classified as a mineral, and its components are used as fuel.

Properties and composition of natural gas

Natural gas is flammable and explosive at a ratio of approximately 10% air. It is 1.8 times lighter than air, colorless and odorless; these properties are due to the high content of gaseous alkanes (CH4 - C4H10). Included natural gas methane (CH4) predominates, it occupies from 70 to 98%, the rest of the volume is filled with its homologues, carbon dioxide, hydrogen sulfide, mercaptans, mercury and inert gases.

Classification of natural gases

There are only 3 groups:

The first of them is almost eliminating the content of hydrocarbons with more than two carbon compounds, the so-called dry gases, obtained exclusively in fields intended only for gas production.
The second is gases produced simultaneously with primary raw materials. These are dry, liquefied gases and gas gasoline mixed with each other.
The third group includes gases consisting of dry gas and a significant amount of heavy hydrocarbons, of which gasoline, naphtha and kerosene are isolated. In addition, the composition contains a small amount of other substances. These substances are extracted from gas condensate fields.

Properties of constituent substances

The first four members of the homologous series under normal conditions are flammable gases that are colorless and odorless, explosive and flammable:

Methane

The first substance of the alkanes series is the most resistant to temperatures. It is slightly soluble in water and lighter than air. The combustion of methane in the air is marked by the appearance of a blue flame. Most powerful explosion occurs when one volume of methane is mixed with ten volumes of air. At other volumetric ratios, an explosion also occurs, but with less force. In addition, a person may suffer irreparable harm if they inhale high concentrations of gas.

Methane can be in solid state of aggregation in the form of gas hydrates.

Application:

It is used as industrial fuel and raw material. Methane is used to produce a number of important products - hydrogen, freons, formic acid, nitromethane and many other substances. To produce methyl chloride and its homologous compounds, methane is chlorinated. Incomplete combustion of methane produces finely dispersed carbon:

CH4 + O2 = C + 2H2O

Formaldehyde appears through an oxidation reaction, and when reacting with sulfur, carbon disulfide appears.

The breaking of methane carbon bonds under the influence of temperature and current produces acetylene, used in industry. Hydrocyanic acid is produced by the oxidation of methane with ammonia. Methane is a derivative of hydrogen in the generation of ammonia, as well as the production of synthesis gas occurs with its participation:

CH4 + H2O -> CO+ 3H2

Used for binding hydrocarbons, alcohols, aldehydes and other substances. Methane is actively used as a fuel for Vehicle.

Ethane

A limiting hydrocarbon, C2H6, is a colorless substance in the gaseous state that produces little light when burned. It dissolves in alcohol in a ratio of 3:2, as they say, “like in like,” but is almost insoluble in water. At temperatures above 600° C, in the absence of a reaction accelerator, ethane decomposes into ethylene and hydrogen:

CH4 + H2O -> CO+ 3H2

Ethane is not used in the fuel industry; the main purpose of its use in industry is to produce ethylene.

Propane

This gas is poorly soluble in water and is a widely used fuel. It produces a lot of heat when burned and is practical to use. Propane is a by-product of the cracking process in the oil industry.

Butane

It has low toxicity, a specific odor, has intoxicating properties, inhalation of butane causes asphyxia and cardiac arrhythmia, negatively affects nervous system. Appears during associated cracking oil gas.

Application:

The undeniable advantages of propane are its low cost and ease of transportation. Propane-butane mixture is used as fuel in populated areas, where natural gas is not supplied, when processing low-melting materials with small thickness, instead of acetylene. Propane is often used in the procurement of raw materials and processing of scrap metal. In everyday life, areas of necessity include space heating and cooking on gas stoves.

In addition to saturated alkanes, natural gas includes:

Nitrogen

Nitrogen consists of two isotopes 14A and 15A, and is used to maintain pressure in wells during drilling. To obtain nitrogen, air is liquefied and separated by distillation; this element makes up 78% of the air composition. It is mainly used to produce ammonia, from which nitric acid, fertilizers and explosives.

Carbon dioxide

Connection passing on atmospheric pressure from solid (dry ice) to gaseous state. It is released during the breathing of living beings, and is also found in mineral springs and air. Carbon dioxide is a food additive used in fire extinguisher cylinders and air guns.

Hydrogen sulfide

A very toxic gas - the most active of the sulfur-containing compounds, and therefore very dangerous for humans due to its direct effect on the nervous system. A colorless gas under normal conditions, characterized by a sweetish taste and a disgusting odor of rotten eggs. It is highly soluble in ethanol, unlike water. Sulfur is obtained from it, sulfuric acid and sulfites.

Helium

This is a unique product that slowly accumulates in the Earth's crust. It is obtained by deep freezing gases containing helium. In the gaseous state, it is an inert gas that has no external expression. Helium is in a liquid state, also odorless and colorless, but can infect living tissue. Helium is non-toxic and cannot explode or ignite, but at high concentrations in the air it causes asphyxiation. It is used when working with metals and as a filler. balloons and airships.

Argon

Noble, non-flammable, non-toxic, without taste or color. It is produced as an escort for the separation of air into oxygen and nitrogen gas. Used to displace water and oxygen to extend the shelf life of food, it is also used in metal welding and cutting.

Methane (swamp gas; CH 4) is the simplest saturated hydrocarbon. Colorless, odorless gas, melting point -182.48°. Methane ignites easily; a mixture of methane and air is explosive.

Methane is the main component of natural gas (60-99%), mine gas (35-40%), as well as various products of anaerobic decomposition of organic substances, such as swamp gas and gases from irrigation fields. IN large quantities methane is formed during the coking of coal, hydrogenation of coal and in other industrial processes.

Methane is used as a fuel for gasification, as well as for the industrial synthesis of hydrocarbons of large mol. weight. With incomplete combustion or catalytic oxidation of methane, it forms methanol (see Methyl alcohol), (see), acetylene (see). Methane is also used in the production of soot, methyl chloride, chlorbromobenzene, nitromethane, and other products.

Methane is found in intestinal gases (as a result of methane fermentation), in the blood of animals and humans.

Methane is the most inert compound from the group of paraffin hydrocarbons. Physiological methane is indifferent and can cause poisoning only in very high concentrations (due to the low solubility of methane in water and blood). At the same time toxic effect methane also appears at lower concentrations of methane in the air. Thus, when the air contains 25-30% methane, the first signs appear (increased heart rate, increased breathing volume, impaired coordination of fine muscle movements, etc.). Higher concentrations of methane in the air cause headaches in humans. The full toxic effect of methane appears only when high blood pressure(2-3 atm).

First aid for acute poisoning: removing the victim from the harmful atmosphere. Hot water bottles. If there is no breathing, artificial respiration is performed immediately (before the doctor arrives), which stops only after signs of rigor mortis appear.

Chronic effects of methane. In those working in or in industries where methane and other hydrocarbons of the methane series are present in the air, noticeable changes in the side have been described (positive oculo-cardiac reflex, pronounced atropine test, ). However, chronic exposure to methane does not cause severe organic changes, although some researchers associate the occurrence of nystagmus in miners with prolonged exposure to methane.

Prevention of methane poisoning. In underground mines, methane content above 0.75 vol.% is not allowed. If the methane content increases, workers must be removed and the premises must be ventilated. The main measure to prevent methane accumulation in mines is the presence of good ventilation. For personal protection, it is necessary to use helmets with forced air supply or breathing apparatus equipped with an air supply.

The carbon atom in the methane molecule is in a state of sp3 hybridization. As a result of the overlap of the four hybrid orbitals of the carbon atom with the s-orbitals of the hydrogen atoms, a very strong methane molecule is formed.
Methane gas is colorless and odorless, lighter than air, slightly soluble in water. Saturated hydrocarbons can burn, forming carbon monoxide (IV) and water. Methane burns with a pale bluish flame: CH4 + 2O2 = 2H2O
When mixed with air (or with oxygen, especially in a volume ratio of 1:2, as can be seen from the reaction equation), methane forms explosive mixtures. Therefore, it is dangerous both in everyday life (gas leakage through taps) and in mines. In case of incomplete combustion methane produces soot. This is how it is produced industrially. In the presence of catalysts, the oxidation of methane produces methyl alcohol and formaldehyde
When heated strongly, methane decomposes according to the equation: CH4=C+2H2
In specially designed furnaces, the decomposition of methane can be carried out to the intermediate product acitelene:
2CH4=C2H 2+3H2
Methane is characterized by substitution reactions. In the light or at ordinary temperature, halogens—chlorine and bromine—gradually (in stages) displace hydrogen from the methane molecule, forming so-called halogen derivatives. Chlorine atoms replace hydrogen atoms in it to form a mixture of various compounds:
CH3Cl-chloromethane (methyl chloride),CH2Cl2-dichloromethane,CHCl3-trichloromethane,CCl4-tetrachloromethane
Each compound can be isolated from this mixture. Chloroform and carbon tetrachloride are important as solvents for resins, fats, rubber and other organic substances.
The formation of halogen derivatives of methane occurs via a chain free radical mechanism. Under the influence of light, chlorine molecules decompose into inorganic radicals: Cl2 = 2Cl
The inorganic radical Cl removes a hydrogen atom with one electron from the methane molecule, forming HCl and the free radical CH3 H H
H:C_| H+Cl=H:C +HCl
H| H
The free radical interacts with the chlorine molecule Cl2, forming a halogen derivative and a chlorine radical:
CH3+Cl_| Cl=CH3-Cl+Cl
Methane at ordinary temperatures is more resistant to acids, alkalis and many oxidizing agents. However, it reacts with nitric acid:
CH4+HNO3=CH3NO2 +H2O
nitromethane
Methane is not capable of addition reactions, since all valences in its molecule are saturated.
The above substitution reactions are accompanied by the cleavage of C-H bonds. However, processes are known in which not only the cleavage of C-H bonds occurs, but also the rupture of the chain of carbon atoms (in methane homologues). These reactions occur at high temperatures and in the presence of catalysts. For example:
C4H10+H2 - dehydrogenation process
C4H10-|
C2H6 + C2H4 cracking

Producing methane.
Methane is widespread in nature. It is the main integral part many flammable gases, both natural (90-98%), and artificial, released during the dry distillation of wood, peat, coal, as well as during oil cracking
Methane is released from the bottom of swamps and from coal seams in mines, where it is formed during the slow decomposition of plant debris without access to air. Therefore, methane is often called swamp gas or mine gas
In laboratory conditions, methane is obtained by heating a mixture of sodium acetate and sodium hydroxide:
200 *C
CH3|COONa +NaO|H=Na2CO3 + CH4|
or when aluminum carbide interacts with water:
Al4C3 +12H2O=4Al(OH)3 +3CH4|
In the latter case, the methane turns out to be very pure.
Methane can be produced from simple substances by heating in the presence of a catalyst: Ni
C+2H2=CH4

And also by synthesis based on water gas
Ni
CO+3H2 =CH4 +H2O
Homologues of methane, like methane, are obtained in laboratory conditions by calcination of salts of the corresponding organic acids with alkalis. Another method is the Wurtz reaction, i.e. heating monohalogen derivatives with sodium metal, e.g.
C2H5 |Br+2Na+Br|C2H5= C2H5-C2H5+2NaBr

In technology, to produce synthetic gasoline (a mixture of hydrocarbons containing 6-10 carbon atoms), synthesis is used from carbon monoxide (II) and hydrogen in the presence of a catalyst (cobalt compound) and at elevated pressure. The process can be expressed by the equation:
200*С
nCO+(2n+1)H2=CnH2n+2+nH2O

Applications of alkanes
Due to its high calorific value, methane is consumed in large quantities as fuel (in domestic gas and in industry. Substances obtained from it are widely used: hydrogen, acitelen, soot. It serves as the starting raw material for the production of formaldehyde, methyl alcohol, as well as various synthetic products
Big industrial value has the oxidation of higher saturated hydrocarbons - paraffins with a number of carbon atoms of 20-25. Synthetic fatty acid with different chain lengths, which are used for the production of soaps, various detergents, lubricants, varnishes and enamels.
Liquid hydrocarbons are used as fuel (they are part of gasoline and kerosene). Alkanes are widely used in organic synthesis.

The chemical properties of methane are no different from the properties inherent in all. In a school chemistry course, methane is studied as one of the first organic substances, since it is one of the simplest representatives of alkanes.

Methane formula and methods for its production

Methane is found in large quantities in the atmosphere. We do not pay attention to the presence of this gas in the air, because it does not affect our body in any way, but canaries are very sensitive to methane.

Once upon a time they even helped miners go underground. When the percentage of methane changed, the birds stopped singing. This served as a signal to the person that he had descended too deep and needed to climb up.

Methane is formed as a result of the breakdown of the remains of living organisms. It is no coincidence that methane is translated from English as swamp gas, because it can be found in swampy reservoirs and coal mines.

The main source of gas in the agricultural sector is cattle. Yes, they remove methane from the body along with other waste products. By the way, an increase in the number of cattle on the planet can lead to the destruction of the ozone layer, because methane and oxygen form an explosive mixture.

Methane can be produced industrially by heating carbon and hydrogen or by synthesizing water gas; all reactions occur in the presence of a catalyst, most often nickel.

In the USA, an entire methane extraction system has been developed; it is capable of extracting up to 80% of gas from natural coal. Today, world methane reserves are estimated by experts at 260 trillion cubic meters! Even natural gas reserves are significantly smaller.

In the laboratory, methane is produced by reacting aluminum carbide (an inorganic compound of aluminum with carbon) and water. Also using, which reacts with sodium acetate, better known as food supplement E262.

Physical properties of methane

Characteristic:

Colorless gas, odorless.
Explosive.
Insoluble in water.
Boiling point: -162 o C, freezing point: -183°C.
Molar mass: 16.044 g/mol.
Density: 0.656 kg/m³.

Chemical properties of methane

Talking about chemical properties ah, they highlight those reactions in which methane enters. They are given below along with the formulas.

Methane combustion

Like all organic substances, methane burns. You can notice that during combustion a bluish flame is formed.

CH 4 + 2O 2 → CO 2 + 2H 2 O

This reaction is called a combustion or complete oxidation reaction.

Substitution

Methane also reacts with halogens. These are chemical elements of group 17 in the periodic table of Mendeleev. These include: fluorine, chlorine, bromine, iodine and astatine. The reaction with halogens is called a substitution or halogenation reaction. This reaction occurs only in the presence of light.

Chlorination and bromination

If chlorine is used as a halogen, the reaction will be called a chlorination reaction. If the halogen is bromine, then bromination, and so on.

CH 4 + Cl 2 → CH 3 Cl + HCl

CH 4 + Br 2 → CH 3 Br + HBr

Chlorination. Lower alkanes can chlorinate completely.

CH 4 + Cl 2 → CH 3 Cl + HCl

CH 3 Cl + Cl 2 → CH 2 Cl 2 + HCl

CH 2 Cl 2 + Cl 2 → CHCl 3 + HCl

CHCl 3 + Cl 2 → CСl 4 + HCl

Likewise, methane can completely undergo bromination reaction.

CH 4 + Br 2 → CH 3 Br + H Br

CH 3 Br + Br 2 → CH 2 Br 2 + HBr

CH 2 Br 2 + Br 2 → CHBr 3 + HBr

CHBr 3 + Br 2 → CBr 4 + HBr

With iodine there is no such reaction, but with fluorine, on the contrary, it is accompanied by a rapid explosion.

Decomposition

This hydrocarbon is also characterized by a decomposition reaction. Full decomposition:

CH 4 → C + 2H₂

And incomplete decomposition:

2CH 4 → C 2 H 2 + 3H 2

Reaction with acids

Methane reacts with concentrated sulfuric acid. The reaction is called sulfonation and occurs with slight heating.

2CH 4 + H 2 SO 4 → CH 3 SO 3 H + H 2 O

Oxidation

As already mentioned, CH 4 can be completely oxidized, but with a lack of oxygen, incomplete oxidation is possible.

2CH 4 + 3O 2 → 2CO + 4H 2 O

CH 4 + O 2 → C + 2H 2 O

Among other things, this gas is characterized by catalytic oxidation. It occurs in the presence of a catalyst. At different ratios of moles of substance, different final reaction products are obtained. Mainly:

alcohols: 2CH 4 + O 2 → 2CO 3 OH
aldehydes: CH 4 + O 2 → HSON + H 2 O
: 2CH 4 + 3O 2 → 2НСООН + 2Н 2 O

The reaction takes place at a temperature of 1500°C. This reaction is also called cracking - thermal decomposition.

Methane nitration

There is also a nitration reaction or the Konovalov reaction, named after the scientist who proved that dilute nitric acid acts with saturated hydrocarbons. The reaction products are called nitro compounds.

CH 4 + HNO 3 → CH 3 NO 2 + H 2 O

The reaction is carried out at a temperature of 140-150°C.

Methane dehydrogenation

In addition, methane is characterized by a dehydrogenation (decomposition) reaction - the detachment of hydrogen atoms and the production of acetylene, in this case.

2CH 4 → C 2 H 2 + 3H 2

Application of methane

Methane, like other saturated hydrocarbons, is widely used in Everyday life. It is used in the production of gasoline, aviation and diesel fuel.

Used as a base for the production of various organic raw materials in enterprises. Methane is also widely used in medicine and cosmetology.

Methane is used to produce synthetic rubber, paints and tires.

Athletes use so-called liquid methane to quickly gain weight in a short period of time.

And when methane is chlorinated, a substance is formed that is subsequently used to degrease surfaces or as a component in nail polish removers. For some time, the product of the interaction of methane and chlorine was used as an anesthesia.

Send your good work in the knowledge base is simple. Use the form below

Students, graduate students, young scientists who use the knowledge base in their studies and work will be very grateful to you.

Posted on http://www.allbest.ru/

1. Physico-chemical properties of methane

methane gas explosive

Methane is a colorless, odorless and tasteless gas. Its relative density relative to air density is 0.55. Poorly soluble in water. Under normal conditions, methane is very inert and combines only with halogens. In small quantities, methane is physiologically harmless. An increase in methane content is dangerous only due to a decrease in oxygen content. However, with a methane content of 50-80% and normal oxygen content, it causes severe headaches and drowsiness.

Methane forms flammable and explosive mixtures with air. When the content in the air is up to 5%, it burns at a heat source with a bluish flame, while the flame front does not spread. At a concentration of 5 to 14 it explodes; above 14 it does not burn or explode, but can burn near a heat source with access to oxygen from the outside. The most complete picture of the explosiveness limits of a methane-air mixture is given by the graph for determining the explosiveness of methane with air (Fig. 1.1).

The greatest explosion occurs when its content is 9.5%. The temperature at the epicenter of the explosion reaches 18750C, the pressure is 10 atm. Methane combustion and explosion occur through the following reactions:

with sufficient oxygen

CH4+2O2 = CO2+2H2O

with a lack of oxygen

CH4+O2=CO+H2+H2O

Methane ignition occurs at a temperature of 650-750 C. Methane has a flash delay property, which means that its ignition occurs some time after contact with a heat source occurs. methane gas explosive

For example, at a methane concentration of 6% and igniter temperatures of 750, 1000, 1100C, the duration of the induction period is respectively 1 s, 0.1 s. and 0.03 s.

The presence of an induction period creates conditions for preventing methane outbreaks during blasting operations through the use of safety explosives. In this case, the cooling time of the explosion products below the ignition temperature of methane should be less than the induction period.

Fig.1 Graph for determining the explosiveness of methane-air mixtures (Sk - oxygen content; Cm - methane content): 1-explosive mixture; 2-non-explosive mixture; 3-mixture that may become explosive when fresh air is added.

2. Origin and types of connection between methane and rocks

The processes of methane formation occurred simultaneously with the formation of coal layers and the metamorphism of primary organic matter. A significant role in this case belonged to fermentation processes caused by the activity of bacteria.

In rocks and coal, methane is found in the form of free and sorbed gas. At current working depths, the main amount of methane (about 85%) is in a sorbed state. There are three forms of communication (sorption) of methane by solid matter:

Adsorption is the binding of gas molecules on the surface of a solid under the influence of molecular attraction forces;

Absorption is the penetration of gas molecules into solid without chemical interaction;

Chemisorption - chemical compound gas and solid molecules.

The main amount of gas sorbed by rocks (80-85%) is in the adsorbed state. When a coal seam is destroyed, this gas goes into a free state and is released into the mine workings within one to two hours. Absorbed methane is released from coal for a long time, and chemisorbed methane remains in coal for a long time (tens of years).

3. Methane content and methane capacity of coal seams and rocks

Methane content is the amount of methane contained in natural conditions per unit weight or volume of coal or rock (m3/t, m3/m3)

The main factors determining the methane content of coal deposits are:

Degree of coal metamorphism;

Sorption capacity;

Porosity and gas permeability of sediments;

Humidity;

Depth of occurrence;

Hydrogeology and coal saturation of the deposit;

Geological history of the deposit.

At modern mining depths, the methane content of coal seams increases with increasing mining depth according to a linear law. However, scientists believe that from a depth of 1200-1400 m this pattern will not be observed. This is due to an increase in temperature and a decrease in the sorption capacity of coal

A distinction is made between actual natural and residual methane content. Natural or, as it is also called, initial methane content is the methane content of coal in the seam before it is exposed. Actual methane content is understood as the amount of methane per unit weight of coal in the exposed seam near the face. It is always less than natural, because when the formation is opened, methane is released. Residual methane content is the amount of methane per 1 ton of coal that remains in coal for a long time. This methane is not released in the mine and is released to the surface.

Methane content is measured in m3/ton of dry ash-free mass and in m3/ton. There is the following relationship between these quantities

Х=0.01 Хг(100-Wp-As)

where X is methane content, m3/t,

Хг - methane content m3/t.s.b.m.;

Wp - coal moisture content %;

As - ash content of coal %.

Methane capacity is the amount of gas in a free and sorbed state that a unit weight or volume of coal and rock can absorb at a given pressure and temperature.

4. Types of methane emissions into mine workings

There are three types of methane emissions into mine workings:

1. Ordinary; Souffle; 3. Sudden discharge with the ejection of coal and sometimes rock.

The usual release of methane occurs from small pores and cracks throughout the surface of the formation, from broken coal and side rocks. The discharge occurs slowly but continuously, it is accompanied by rustling, slight crackling and hissing. Methane release from the exposed surface of the seam and from broken coal is described by the equality

I(t)=I0*е-кt; m3/min (1)

where I(t) is methane release from broken coal or a freshly exposed surface of the seam t minutes after exposure;

I0-methane release at the initial moment after exposure of the seam or coal mining;

e-base of natural logarithm;

k-experimental coefficient characterizing the physical and mechanical properties of the formation;

t-time elapsed from the moment of exposure of the seam or coal mining, min.

However, the dynamics of methane release from broken coal and the exposed surface of the seam are different. Degassing of broken coal practically ends 2-3 hours after breaking, and of the exposed surface of the seam 2-3 months after exposure.

Ordinary methane emission is uneven over time and depends on many factors: the operation of excavation mechanisms, blasting operations, planting roof rocks, degassing work, ventilation mode of areas, etc. The unevenness of methane emission is characterized by an unevenness coefficient, which is equal to the ratio of the maximum methane emission to the average t .e.

For Donbass conditions Kn=1.43-14

MakNII research has proven that methane release in the outgoing stream of the working face and excavation area is a random variable in time. In this case, with sufficient accuracy for practice, the maximum and average methane release can be determined based on the use of the normal distribution law random variable, Whereby

where is the standard deviation of the measured methane emission values. To determine the Imax values in both the outgoing stream of the site and the working face, it is necessary to carry out 3-day observations with an interval of measuring methane concentration and air flow of 30 minutes.

Breathing methane emissions are the release of methane in large quantities with characteristic noise from visible cracks and voids in side rocks and coal seams. The effect of breathers can be short-term, but usually long-lasting, even up to several years. There are soufflers of the first and second kind. Breathers of the first kind include breathers of geological origin, which, as a rule, are confined to zones of tectonic disturbances.

Breathers of the second type include those of a mining production nature. These breathers occur as a result of partial unloading of coal seams and interlayers located in the soil and roof of working seams in the zone of influence of mining operations.

The danger of breathers is that they appear suddenly, and in a short period of time, possibly the formation of explosive concentrations of methane-air mixture in large volume. To combat breathers, preliminary degassing of the massif is carried out through the use of advanced drilling, advanced development of protective layers, an appropriate method of roof control, the amount of air supplied to mines dangerous due to breathers is increased, and gas is captured. When capturing gas, a sealed kiosk (made of brick or cinder block) is constructed at the mouth of the breather, from which the gas is discharged through a pipeline either into the general outgoing stream of the wing, shaft, or to the surface.

Sudden releases of methane occur during various gas-dynamic phenomena, which include:

Sudden emissions of coal and gas;

Sudden eruptions turning into sudden outbursts on steep seams;

Sudden gas breakthroughs with small amounts of coal fines;

Rock bursts with coal extraction and associated gas release;

Spilling and collapse of coal with associated gas release;

Collapse of the main roof with intense gas release in the goaf;

Coal eruptions that occur during concussive explosions on steep seams, turning into sudden outbursts of coal and gas;

Rock emissions resulting from the explosion of a mountain range with associated gas release.

Of the gas-dynamic phenomena listed above, the most dangerous are sudden emissions of coal and gas. When there is a sudden release from a coal seam into a working, in a short period of time (several seconds), a large number of gas and a significant amount of coal and sometimes fine rock is released. In 1973, at the Gagarin mine in Gorlovka, up to 180 thousand m3 of methane was released during the release and up to 14 thousand tons of coal were taken into production.

The nature and mechanism of sudden emissions have not yet been thoroughly studied. Currently, the most recognized hypothesis is that a sudden outburst occurs under the complex action of rock pressure, the stressed state of the coal mass and gas pressure.

5. Combating methane using ventilation

Selection of a rational ventilation scheme for given mining and geological conditions;

Supply of the required amount of air to excavation areas, production and preparation faces, as well as other objects consuming the required amount of air;

Isolated removal of methane by means of ventilation into the outgoing stream or outside the excavation area.

Choosing a rational ventilation scheme

When choosing a ventilation scheme for an excavation area, it is necessary to ensure that the selected scheme meets the following requirements:

1. The most complete separate dilution of methane released from all sources;

Ensuring the maximum load on the production face in terms of the gas factor and the minimum cost of coal in terms of the ventilation factor;

3. Ensuring the possibility of conducting degassing work;

4. Providing ventilation maneuvers in case of accidents;

5. Reliability of ventilation in normal and emergency modes;

6. Ensuring the most favorable sanitary and hygienic working conditions.

Fulfilling all these requirements is a very complex mining and technical task.

Currently, in the practice of mine ventilation, there are about 80 different schemes for ventilation of excavation areas. DonUGI has developed a classification of all ventilation schemes for excavation areas, which is presented in the Coal Mine Ventilation Design Guide.

From the point of view of ensuring the maximum load on the production face, all ventilation schemes can be divided into 4 groups:

1. Return ventilation schemes for the ventilation drift in the mined-out space. These schemes are characterized by the fact that the magnitude of the load on the face depends on whether methane from the mined-out space comes to the interface between the longwall and the ventilation roadway or is carried out to the ventilation roadway, bypassing the interface.

Posted on http://www.allbest.ru/

Fig. 2 Scheme of ventilation of the excavation area of type 1-V-N-v-v.

Iuch=Ipl+Ivp

Ioch=Ipl+ Kvp*Ivp

Amax=f (Ipl+Kvp*Ivp)

2. Return ventilation schemes for a ventilation drift in a coal massif

Posted on http://www.allbest.ru/

3. Direct-flow ventilation schemes for the ventilation drift in the mined-out space with the illumination of the outgoing ventilation stream.

Posted on http://www.allbest.ru/

Fig.4 Scheme of ventilation of the excavation area of the 3-V-N-v-f type.

4. Direct-flow ventilation schemes for a ventilation drift in a coal mass with illumination of the outgoing ventilation stream

Posted on http://www.allbest.ru/

Fig. 5 Scheme of ventilation of the excavation area of type 2-M-N-v-vt.

In each specific case, the choice of a rational ventilation scheme for the excavation area is decided on the basis of a technical and economic comparison of possible options.

Supply of the required amount of air to the areas and working faces.

The amount of air that needs to be supplied to the excavation area depends on methane release and is determined by the formula

Qch=, m3/min (5)

where Iuch is the absolute methane abundance of the excavation area, m3/min;

Kn - coefficient of unevenness of methane release;

C is the permissible PB concentration of methane in the outgoing stream of the area, %;

C0 is the concentration of methane in the air stream entering the site.

However, in many cases it is not possible to supply the required amount of air to the excavation areas and working faces. This may be for the following reasons:

1. The actual aerodynamic resistance of the ventilation network exceeds the design one, and therefore the selected fan cannot provide the shaft and areas with the required amount of air.

Posted on http://www.allbest.ru/

Fig.6 Fan performance Qп, Qф when operating on a network with design resistance Rп and actual Rф.

The air supply to the working face and to the excavation area is limited by the speed of air movement in the face, which, according to the safety regulations, should be no more than 4 m/s.

Isolated methane discharge into the outgoing stream or outside the excavation area

Reducing methane concentrations can be achieved through isolated methane removal into the outflow stream or outside the excavation area. Let's consider some schemes for isolated methane removal into the outgoing stream and outside the excavation area.

Scheme No. 1 - Isolated methane removal through a pipeline outside the excavation area using a gas suction fan installation in a pillar mining system.

Posted on http://www.allbest.ru/

Fig. 7 Isolated methane removal through a pipeline outside the excavation area using a gas suction fan installation in a pillar mining system.

Scheme No. 2 Scheme of isolated methane removal outside the excavation area with 1 fan; 2-suction pipeline; 3-suction pipes; 4-mixing chamber; 5-ventilation jumper; 6-coal pillars or rubble strip

Posted on http://www.allbest.ru/

Fig. 8 Isolated methane removal outside the excavation area with a continuous mining system.

3. Schemes for ventilation of excavation areas with isolated removal of methane from mined-out spaces through unsupported workings

Posted on http://www.allbest.ru/

Fig.9 a - Scheme using local excavation

Posted on http://www.allbest.ru/

Fig. 9 b - Scheme using workings of previously mined longwalls.

Posted on http://www.allbest.ru/

Fig. 9 c - Isolated methane removal using previously mined longwall workings

4. Isolated removal of methane from the mined-out space into the outgoing stream of the area through pipelines using special installations such as USM-02 and UVG-1

These installations are used to reduce the concentration of methane at the interface between the longwall and the ventilation drift.

Posted on http://www.allbest.ru/

Fig. 10 Isolated removal of methane from the mined-out space into the outgoing stream of the area through pipelines using special installations of the USM-02 and UVG-1 type

The schemes of the USM-02 and UVG-1 installations are similar and differ in that the USM-02 installation is used when the methane abundance of the goaf is up to 1.5 m3/min, and the UVG 1 installation has a more powerful fan and is used when the methane abundance of the goaf is up to 3 m3/min.

Calculation of air flow for ventilation of the excavation area with isolated methane removal beyond its boundaries, selection of removal means and safety measures

Calculation of air flow for isolated removal of MAF from the mined-out space through a pipeline using a gas suction unit is carried out according to the formula:

Qch=Qh.w+Qtr (6)

where Qch is the air flow rate in the air supply tunnel, m3/min;

Qv.w - air flow in the ventilation shaft, m3/min;

Qtr is the air flow rate at the suction of the gas suction pipeline, m3/min;

Air flow in the ventilation shaft and pipeline is determined by the formulas

where Iuch is the average expected methane release at the excavation site, m3/min;

KV.P.-coefficient that takes into account the share of methane release from the mined-out space in the gas balance of the excavation area;

Coefficient taking into account the efficiency of isolated methane removal, fraction of units; is taken equal to 0.7 for circuits of type 1-M and 0.3-0.4 for circuits of type 1-B;

CM is the permissible concentration of methane in the pipeline; taken equal to 3%;

KD.S-coefficient, taking into account the efficiency of degassing of adjacent layers, fractions of units; adopted in accordance with the “Guidelines for degassing of coal mines”.

Safety measures when operating gas suction units.

The gas extraction unit must operate continuously. Its shutdown is allowed only during preventive inspections and repairs.

Whenever the gas exhaust fan stops, the electricity in the area served by the installation must be automatically turned off. The gas suction pipeline must be closed with a damper, and a window must be open to ventilate it.

The chamber of the gas exhaust fan must be ventilated with a fresh stream of air; the methane concentration in the chamber must be controlled by a stationary automatic device that removes voltage from electrical equipment at a methane concentration of 1%.

The gas suction unit must be serviced by a driver who has undergone special training.

The driver is obliged:

1. Carry out shift monitoring of the condition of the fan, pipeline and mixing chamber;

Measure the methane content in the pipeline near the fan at least once an hour and at least 3 times per shift in the pipeline near the lava;

3. Ensure air supply from the drift to the pipeline using a control window near the face so that the methane concentration in the pipeline near the fan does not exceed 3%, and in the pipeline near the face 3.5%.

4. Turn off the gas exhaust fan when the main fan stops or if there is a fire in the area; shut off the pipeline near the longwall when the fan is not working and open the control window to ventilate it. Restarting the fan is allowed only after the methane concentration in the chamber has decreased below 1% and in the pipeline near the fan to 3%.

If the methane concentration at the outlet of the mixing chamber reaches 2% or more, and in the pipeline at the lava exceeds 3.5% and at the fan 3%, then measures must be taken to increase the air flow in the chamber and the pipeline.

In the excavation where the mixing chamber is located, 15-20 m from it along the ventilation stream, the methane content should be monitored with a stationary automatic device. The methane sensor is installed against the wall on the side where the mixing chamber is located and must provide telemetry with registration on a recorder.

6. Combating methane with degassing means

6.1 General provisions on degassing of coal mines

The main sources of methane in coal mines are mined seams, underworked, overworked seams and interlayers, as well as host rocks. The share of each of these sources is reflected in the gas balance of the excavation areas and depends on the mining, geological and mining conditions

Mine degassing is a set of measures aimed at extracting and capturing methane released from all sources, with isolated removal to the surface (capture), and also providing for physical or chemical binding of methane before it enters the mine workings.

The criterion determining the need for degassing is an increase in the methane content of workings If above the permissible ventilation factor Iр

Iph > Iр=,m3/min (10)

V-permissible according to PB maximum speed air movement in lava, m/s;

S-minimum cross-sectional area of the longwall according to the fastening passport, free for air passage, m

The degassing efficiency coefficient, at which conditions that are normal in terms of the methane emission factor are ensured, is determined by the formula

The effectiveness of degassing largely depends on which layers and host rocks are degassed, unloaded or not unloaded from rock pressure. When the layers and host rocks are partially unloaded from rock pressure, the gas passes from the sorbed state into the free state and degassing is effective.

6.2 Methods for degassing formations and host rocks not relieved from rock pressure

6.2.1 Degassing during capital and development workings

Degassing of the host rocks and the coal mass surrounding the excavation during capital mining operations must be used when methane release into the excavation is 3 m3/min or more.

When carrying out vertical workings of shafts, boreholes, pits, degassing wells with a length of 30-100 m and a diameter of 80-100 mm are drilled from the surface or from special drilling chambers arranged on the sides of the passable workings. The protected zone is 7-8 m larger than the diameter of the shaft or other vertical excavation. When drilling wells, a methane-bearing coal seam or layer of gas-containing rock must be drilled at full capacity.

When drilling wells from the surface, 6-9 wells are drilled around a circle, the diameter of which is 5-6 m larger than the diameter of the trunk. The wells are sealed and connected to a degassing gas pipeline and a vacuum pump. In degassing wells, a vacuum of 150-200 mm Hg is created. Art. and degassing of strata and gas-containing rocks occurs.

When degassing from the bottom of the shaft, 9 wells are drilled in the form of a fan from the drilling chambers. The direction of the wells is chosen so that the bottoms of the wells intersect the gas-containing layer in a circle, the diameter of which should be 7-8 m larger than the diameter of the shaft. The wells are connected to a degassing pipeline, and the coal-bearing strata is degassed.

When opening a layer of gas-containing rock or a methane-bearing coal seam with crosscuts, degassing wells with a diameter of 80-100 mm are drilled through the gas-containing layer or coal seam until they completely intersect. Wells are drilled from chambers passed along the sides of the workings at a distance of 3-5 m normal to this layer or formation. Number of wells 5-10. The drilling direction is chosen so that the wells intersect gas-bearing rocks along a circle with a diameter of at least one and a half and no more than three diameters of the excavation being carried out. The wells are cased to a depth of at least 2-5 m and connected to the gas pipeline. Gas suction should be carried out under a vacuum of 100-200 mmHg.

Posted on http://www.allbest.ru/

Fig. 11 Diagram of the location of wells when opening the formation with a cross-cut

6.2.2 Degassing during horizontal and inclined workings in coal seams

Degassing is carried out when methane release into the mine is more than 3 m3/min. When the length of the excavations is up to 200 m, barrier wells are drilled along the entire length of the future excavation. For longer excavation lengths, wells are drilled from chambers on both sides of the excavation at a distance of 1.5-5 m from its wall. The length of the wells is up to 200 m, the diameter is 50-100 mm. The vacuum in degassing wells should be maintained within 100-150 mm. rt. Art.

6.2.3 Degassing of mined coal seams with wells drilled from workings

This method is used when preparing the formation for excavation, both with pillar and continuous mining systems, if there is a sufficient advance in the development workings. Preference should be given to upwelling wells, as they are 20-30% more efficient than downwelling ones. When drilling, it is necessary to take into account the direction of the main system of cleavage cracks. Wells drilled perpendicular to the main fracture system are 10-30% more efficient and reduce the duration of degassing.

Schemes for degassing developed coal seams using wells drilled from workings are divided into 2 groups:

A-degassing wells are drilled in the plane of the formation from the formation development workings along the upslope, dip, strike or at a certain angle to the strike line;

B-degassing wells are drilled from development or capital workings through the rock mass into the cross of the strike of the formation. This group of schemes is used mainly in steeply dipping formations.

With both groups of schemes, a parallel single, fan or cluster arrangement of degassing wells is possible. For group A schemes, parallel single wells are more effective, since they degass the coal seam relatively evenly and can be used to inject water into the seam and moisten the coal mass in order to prevent sudden outbursts of coal and gas and reduce dust formation.

When choosing a scheme for degassing the developed formation with wells in the conditions of the most common pillar and continuous development systems, it is necessary to be guided by the following provisions:

a) Give preference to raised parallel-single wells with their parallel location relative to the line of the production face.

The fan arrangement of reservoir degassing wells should be adopted in exceptional cases when it is impossible to drill single wells in parallel. For example, in zones of geological disturbances.

b) Accept the following geometric parameters in parallel to single wells drilled through the formation:

well diameter - 80-150 mm;

The length of the wells should be set depending on the development conditions:

if the formation area is contoured by development workings, then the length of the well is taken to be 10-15 m less than the longwall length for upward or horizontal wells and equal to the floor height for downward wells; in the latter case, the wells are sealed from their mouth and bottom.

If the seam section is not contoured, there is one development working from which the coal mass is drilled, then the length of the wells is taken to be 10-15 m longer lava.

The distance between parallel single wells is taken in accordance with the calculation depending on the required efficiency and duration of degassing. For the conditions of the Donetsk basin, the distance between wells can be approximately determined by the formula

where t is the duration of formation degassing, days; (150-180 days)

Kdeg.pl - the required efficiency of formation degassing.

c) sealing of wellheads should be done with special sealants or cement-sand mortar. Reservoir wells should be sealed to a depth of 4-10 m, and wells drilled across the strike of the formation through the rock mass - 2-5 m.

In conclusion, it should be noted that the efficiency of degassing of seams not relieved of rock pressure is insignificant, and as a rule is 20-30%, and only when degassing coals that have high porosity and permeability can it reach 40-50%.

6.3 Degassing of adjacent coal seams (satellites) and host rocks during their undermining and overworking

6.3.1 Basic theory of satellite degassing

Let's consider a suite of layers K1-K5, lying at depth H, of which the K layer is developed. At the indicated depth, the K2 layer has been developed along the AB span over a significant area. At an arbitrary point “C”, located under the undeveloped part of the K2 formation, the gas pressure is less than the weight of the column of overlying rocks, therefore, in this zone, gas is not released from the K1 formation. At point “E”, located under the mined-out area of the K2 formation, the rock pressure on the K1 formation drops to the weight of the rock column between the K1 formations. K If this pressure is less than the gas pressure in the K1 formation, the gas gradually passes into a free state, deforms the rocks between the layers, resulting in a cavity n1 is formed in which free gas accumulates. In the cavity, the gas pressure gradually increases, and if the gas pressure turns out to be greater than the resistance of the rocks between the layers, the rocks break through. Gas from satellite K1 enters the workings of formation K through the cracks formed.

The K3 layer, which lies above the developed K2 layer and is located below the line of random collapse of the KN, almost completely releases gas into the workings of the K2 layer. Degassing such a layer with wells is not effective and makes no sense.

Posted on http://www.allbest.ru/

Fig. 12 Satellite drainage diagram

The K4 layer, located in a zone of smooth losses with a break in the continuity of rocks above the line of random collapse, can also release gas into the workings of the K layer. A cavity is also formed between the satellite K4 and its soil n If the resistance of the rocks between the satellite and the collapse boundary is less than the gas pressure in the cavity n2, gas breaks through this thickness and enters the workings of the developed formation. Degassing of such formations is quite effective.

Satellite K5, which is located in a zone of smooth troughs without breaking the continuity of rocks, is partially unloaded from rock pressure. Consequently, the gas located in the coal from the sorbed state passes into the free state and accumulates in cavity n3. As the K2 seam is mined and the rocks in the goaf are compacted, the continuity of the rocks between the K5 satellite and the boundary of the collapse zone may be disrupted. Gas from the K5 satellite will flow into the workings of the K formation

Practice shows that satellites located in the soil of a developed formation release gas if the distance from the formation to the satellite does not exceed 30-35 m.

Satellites located in the roof of the developed formations are degassed if the distance from the formation to the satellite is not more than 60-70 times the thickness of the developed formation.

6.3.2 Degassing schemes for adjacent coal seams and host rocks

Intense gas release from adjacent coal seams occurs in a partial unloading zone, which captures roof and soil rocks at a certain distance from the seam being mined. In terms of rise and fall, this zone is limited by the unloading angles w, and along strike it begins at some distance behind the production face and moves after it. The angle between the bedding plane of the developed formation and the boundary plane of the beginning of unloading of the undermined massif, drawn along the line of the production face, is 50-850 and depends on the strength, thickness of the layers and lithological composition of the rocks.

The degassing patterns of satellites and rocks of gentle, inclined and steep dip are very diverse. Wells can be drilled from a haulage or ventilation shaft or simultaneously from a haulage and ventilation shaft, with or without a turn towards the production face. The choice of degassing scheme in each specific case is determined by the mining and technical parameters of seam development and the conditions of degassing work. However, in all cases it is necessary to determine the degassing parameters:

Well locations;

Well angles;

Length and diameter of wells;

Diameter of degassing pipeline and type of vacuum pumps.

When degassing undermined strata, it is necessary to take into account the fact that 3 zones are formed in the undermined strata; random collapse, rock deflections with a break in their continuity, and deflections without a break in continuity. Wells must be laid in such a way that they are not overworked and function for a long time.

Determine the angle and length of degassing wells for satellite K4 during development of the K1 formation. Wells are drilled from a haulage drift without turning towards the production face. The diagram for determining well parameters is presented in Fig. 13

Posted on http://www.allbest.ru/

Fig. 13 Scheme for calculating satellite degassing parameters

Legend:

1-zone of random collapse;

2-zone of smooth depressions with a discontinuity of rock continuity;

3-Zone of smooth deflections without breaking the continuity of rocks;

M is the normal distance from the developed formation to the satellite;

b-size of the rear sight or rubble strip according to the uprising;

c-size of the console;

Unloading angle;

Formation dip angle;

Well angle;

lwell is the length of the well.

Formulas for calculation

Posted on http://www.allbest.ru/

7. Sudden outbursts of coal and gas and measures to combat them

7.1 Basic theory of sudden outbursts of coal and gas

To effectively combat sudden outbursts of coal and gas, it is necessary to know the reasons that cause these phenomena, as well as the locations and zones in which they can be expected to occur.

The nature and mechanism of sudden emissions have not yet been thoroughly studied. There are three groups of hypotheses explaining the occurrence of sudden emissions of coal and gas.

The first group includes hypotheses in which the main role in the emission of coal is given to the gas pressure contained in the coal.

The second group includes hypotheses in which the main role in coal emissions is assigned to rock pressure and the stress state caused by both rock pressure and geological conditions.

The third group includes hypotheses in which the main role in the ejection of coal is given to the complex action of rock pressure and gas, with the first influencing the destruction of coal, and the second influencing the emission of destroyed coal.

The most recognized at present is the hypothesis of the 3rd group developed by V.V. Khodot, according to which a sudden outburst occurs due to an abrupt change in the stressed state of the coal seam, a sharp increase in gas release, resulting in the formation of a flow of coal suspended in gas (Fig. 15) .

Posted on http://www.allbest.ru/

P1, y1 - diagram of the pressure and stress state of the massif around the workings after some time has passed after removing a strip of coal or blasting;

P2, y2 - diagram of the pressure and stress state of the massif around the workings at the time of removing a strip of coal or conducting blasting operations;

P3, y3 - diagram of the pressure and stress state of the massif around the workings at the moment of a sudden release of coal and gas.

7.2 Measures to combat sudden emissions of coal and gas.

7.2.1 Methods of combating sudden emissions, their purpose and scope

Measures to combat sudden emissions of coal and gas are aimed at:

Extraction of gas contained in coal;

Gas exhaust braking;

Increasing the plasticity of coal;

Relieving the coal mass from dangerous stresses and increasing its filtration properties;

Strengthening of coal massif;

Inhibition of the ejection process in its initial stage.

According to the conditions of application - directly in the working face or in front of it, regardless of the conduct of mining operations, methods of combating sudden emissions are usually divided into regional and local.

Regional measures include: priority mining of protective seams and preventive moistening of coal seams. Regional activities are carried out before the start of coal seam excavation and allow the seam to be processed over a large area.

Local measures include: moistening the coal mass, hydrosqueezing of coal, hydro-loosening of the seam, hydraulic washing out of leading cavities and cracks, torpedoing of the seam, shock blasting, drilling of leading wells of various diameters.

All of the listed local activities are carried out during reservoir development and require drilling wells. At the same time, it is known that sections of seams that are dangerous due to sudden outbursts are composed of intensively crushed coal, through which drilling wells is an extremely labor-intensive process. Deviation from drilling parameters reduces the effectiveness of activities.

7.2.2 Regional measures to combat sudden releases of coal and gas

Preventive moistening of coal seams dangerous due to sudden outbursts

Hydraulic treatment of coal seams allows you to control their gas dynamics. Thus, slow saturation of the formation with water without changing its filtration characteristics leads to conservation of the gas contained in it. In this case, the pressure and injection rate should not exceed the natural ability of the massif to accept liquid. The physical process of preserving methane in coal with water proceeds as follows. Water injected into the formation under pressure first moves along cracks and large pores, then, under the action of capillary forces, gradually penetrates into transition pores and micropores. The liquid contained in them inhibits the release of gases from the exposed massif and broken coal. Gas release from wells is reduced by 10-15 times, and from broken coal by 2-3 times.

With intensive injection, the filtration characteristics of the formation change, which leads to its preliminary degassing. In this case, the pressure and injection rate exceed the natural capacity of the formation to accept fluid. Injection under pressure exceeding the vertical component of stress from the weight of the overlying rocks causes hydraulic fracturing and hydraulic erosion of the formation.

Discharge parameters: humidification radius - 10-15 m, pressure - 150-200 atm, discharge rate from 3 to 15 l/min.

Development of protective layers

Seams that have a neutralizing effect when mined ahead of dangerous ones are called protective.

The essence of the protective effect of advanced undermining or overmining of a seam dangerous due to sudden outbursts lies in its partial unloading from the pressure of overlying rocks, as a result of which the coal seam expands, its porosity increases, and therefore gas permeability. As a result of unloading of the formation, the gas pressure in it decreases, the sorbed gas passes into a free state and is degassed through the rock mass into the workings of the protective formation.

To ensure the effectiveness of advanced mining, the advance of the excavation of the protective seam in relation to the face of the haulage drift in the dangerous seam must be at least twice the distance between the seams, counting along the normal to the seam. In this case, when mining the upper steep protective layer, not only the production face is protected, but also the face of the haulage drift, and when the thickness of the rocks between the layers is up to 60 m, work is allowed without additional measures to prevent sudden outbursts. With greater thickness of rocks between layers, outbursts are possible, but of less intensity. In these cases, BOPs require additional emission control measures. If the protective steep layer lies in the soil, then the lower part of the longwall and the face of the haulage drift are unprotected. The size of the unprotected zone is 0.55*M, and if the thickness of the interlayer rocks is more than 10 m in the unprotected zone, it is necessary to apply additional measures to combat emissions. The scheme for undermining and overworking of dangerous seams at a steep drop is shown in Fig. 16

Posted on http://www.allbest.ru/

Fig. 16 Scheme for constructing protective zones for steeply dipping layers

Designations adopted in Fig. 16:

b-protection angles, degrees; are adopted according to the “Instructions for the development of seams prone to sudden outbursts of coal, rock and gas” depending on the angle of incidence of the seam (в = 70-800);

S-dimension of the protected zone normal to the formation, m

d1-coefficient taking into account the thickness of the protective layer;

d2-coefficient, taking into account the percentage of sandstones in the interlayer rocks;

S, S-size of the protected zone, respectively, during undermining and overworking without taking into account the thickness of the protective layer and the percentage of sandstones in the interlayer rocks, m; accepted depending on the length of the working face and the depth of development according to the “Instructions”

Determination of protected zones when mining flat-dip seams

With a gentle dip, according to MakNII, protective layers are those located above the dangerous one at a distance of up to 45 m, and below the dangerous one at a distance of up to 100 m.

When undermining or overmining a dangerous flat seam, the zone protected from emissions on the downward and uprising sides is located at a distance of 0.1-0.15 M from the vertical planes passing through the upper and lower boundaries of the cleaning work of the protective seam. Calculation of the size of protection zones for gently dipping formations is carried out using the same methodology as for steeply dipping formations.

Fig. 17 Scheme for determining protection zones for gently dipping formations

7.2.3 Local measures to combat sudden releases

Hydro-loosening of coal seam

Hydroloosening is carried out with the aim of partially degassing the formation and reducing the stressed state of the massif near the mine opening.

The hydroloosening process is as follows. Wells are drilled 6-12m long, with a diameter of no more than 80mm and sealed to a depth of 4-8m. Water is injected into the wells under pressure (0.75-2) gN at a speed of 3 l/min. Water consumption is at least 20 tons of processed massif. The distance between the wells is 6-12m, the value of the irreducible advance is 2-3m. Hydro-loosening is used in production and development faces

Coal seam hydrosqueezing

Hydrosqueezing has the same goals as hydroloosening. It is used in all excavations except those raised at an angle of more than 250.

Holes 2-3 m long are drilled. They are sealed to a depth less than the length of the hole by 0.3 m. The distance between the holes is 4-6 m. Water is injected into the wells. Maximum water pressure

Рmax=(0.8-2)gN + Рс kg/cm2,

and the final one at which the hydrosqueezing process ends

Рkon=30+Рс, kg/cm2

where Рс is the pressure loss in the network

The water injection rate is determined by the formula

Vn?25*m, l/min

Hydrosqueezing is considered effective if the coal face extension is:

In production faces?l=0.01 lg;

In preparatory faces?l=0.02 lg;

where lg is the depth of sealing, m

The irreducible advance for production faces is at least 0.7 m, for preparatory faces - 1.0 m.

Hydraulic washing of leading cavities

It is used when carrying out preparatory workings in seams that have a disturbed pack of coal with a strength of no more than 0.6 and a thickness of at least 5 cm. The height of the cavity is 5-25 cm, the width is not less than 25 cm, the width of the pillars between the cavities is not more than 30 cm. (Fig. 18) The length of the cavities is determined by the formula

Lп?2*lн.о., m

where ln.o is the irreducible advance of the cavities; accepted at least 5 m.

Water pressure when washing cavities 50-100 kg/cm2 (atm), water flow 15-30 l/min

Posted on http://www.allbest.ru/

Fig. 18 Layout of leading cavities

In addition to the local measures discussed above, the following can be used to combat sudden emissions:

Formation of unloading slots and grooves;

Drilling of advanced wells;

Torpedoing of a coal mass and concussive blasting.

7.3 Forecast of outburst hazard of coal seams

The forecast of outburst hazard of coal seams is made at the following stages of field development:

1. During geological exploration work;

When opening up layers with shafts, crosscuts and other field workings;

3. When conducting preparatory and cleaning work.

The forecast of outburst hazard of formations during geological exploration is carried out by geological exploration organizations in accordance with special guidelines agreed upon with MakNII. The forecast of outburst hazard of formations at the opening site is made in the following order:

To exclude the possibility of unexpected opening of the formation, exploration wells are drilled, and the explored rock thickness between the formation and the working must be at least 5 m;

When the face of the opening working approaches at a distance of at least 3 m normal to the coal seam, exploration wells are drilled to take coal samples, and the outburst hazard of the seam is determined based on the following indicators:

Release of volatile substances, %;

Ash content of coal,%;

Initial gas release velocity;

Destructibility of core, mm-1;

Gas pressure, kg/cm2;

Gas release rates, l/min;

Reservoir thickness, m;

The number of coal packs.

Outburst hazard is determined by a scale of outburst hazard signs, which takes into account and encodes all the signs noted above. For example: gas pressure in the formation is up to 35 atm. It is coded as “0” and is considered not dangerous if the pressure is more than 35 atm. number “1” and is considered dangerous, etc.

The formation is considered non-hazardous if the number of dialed “0s” is greater than the number of dialed “1s” by at least. In all other cases, the formation is considered dangerous.

Current forecast of formation outburst hazard

The forecast for seismic-acoustic activity of the formation is as follows:

The average value of hourly noise (pulses/hour) is determined at a reference interval of 30 hours.

A sign of a face entering the danger zone is considered to be a steady increase in the average noise value by 5-10% compared to the previous value at least 2 times in a row. This feature is called the “two-point criterion.”

In addition to a steady increase in the average noise level, a sign of danger is a sudden increase in hourly noise by 4 times or more compared to the average noise level. This sign is called the “critical excess criterion”. The mine management is immediately notified of this.

When determining noise, a geophone is installed in a hole at least 2 m long, drilled through a layer from a leading working. The minimum distance from the working face to the geophone must be at least 3 m. The maximum is no more than the range of the geophone.

The current forecast of outburst hazard based on the initial rate of gas release from boreholes is as follows:

1. Holes 3.5 m long are drilled. 2 holes are drilled in the development workings at a distance of 0.5 m from the working wall. In the working faces, the blast holes are placed at a distance of 0.5 m from the corners of the niches, and in the rest of the longwall - at 10 m from each other.

The zone is classified as dangerous if it is measured in at least one of the holes at a depth of 3.5 m. starting speed gas emissions 5 l/min or more.

Literature

1. K.Z. Ushakov, A.S. Burchakov “Aerology of mining enterprises” M. “Nedra” 1987.

2. K.Z. Ushakov, A.S. Burchakov “Mine aerology” M. “Nedra” 1978.

3. G.L.Pigida, E.A. Budzilo, N.I. Gorbunov “Aerodynamic calculations for mine aerology in examples and problems”, Kyiv 1992.

4. F.A. Abramov, V.A. Boyko “Laboratory workshop on mine ventilation” M. “Nedra” 1966.

5. Guidelines for the design of ventilation in coal mines. Kyiv 1994.

6. Progressive technological schemes for developing seams in coal mines. Part 1, M., 1979.

Posted on Allbest.ru

...

What else to read

No-bake marshmallow cake recipe Many people think that making cakes is a labor-intensive and exhausting process. There are a lot of recipes that will dispel...

Vegetable casserole in the oven - recipes with photos Baked vegetables as such are an indispensable component of most diet menus. If you cook them in the oven together...

Predators and prey. Predators and their prey. Who are the predators Nature simply forces some creatures to hunt others. Moreover, some predators are noticeably more ferocious than others. It even comes...

What substances are obtained from methane. Physicochemical properties of methane

Properties and composition of natural gas

Classification of natural gases

There are only 3 groups:

Properties of constituent substances

Methane

Ethane

Propane

Butane

Nitrogen

Carbon dioxide

Hydrogen sulfide

Helium

Argon

Methane formula and methods for its production

Physical properties of methane

Chemical properties of methane

Application of methane

Send your good work in the knowledge base is simple. Use the form below

Similar documents

What else to read

THE LAST NOTES

What substances are obtained from methane. Physicochemical properties of methane

Properties and composition of natural gas

Classification of natural gases

There are only 3 groups:

Properties of constituent substances

Methane

Ethane

Propane

Butane

Nitrogen

Carbon dioxide

Hydrogen sulfide

Helium

Argon

Methane formula and methods for its production

Physical properties of methane

Chemical properties of methane

Application of methane

Send your good work in the knowledge base is simple. Use the form below

Similar documents

What else to read

THE LAST NOTES

Categories