Anthropotoxins;

Products of destruction of polymeric materials;

Substances entering the room with polluted atmospheric air;

Chemical substances released from polymeric materials, even in small quantities, can cause significant disturbances in the condition of a living organism, for example, in the case of allergic exposure to polymeric materials.

The intensity of the release of volatile substances depends on the operating conditions of polymer materials - temperature, humidity, air exchange rate, operating time.

A direct relationship between the level of chemical pollution has been established air environment from the total saturation of the premises polymer materials.

A growing organism is more sensitive to the effects of volatile components from polymeric materials. Increased sensitivity of patients to the effects of chemical substances released from plastics compared to healthy ones. Studies have shown that in rooms with a high saturation of polymers, the population’s susceptibility to allergies, colds, neurasthenia, vegetative dystonia, and hypertension was higher than in rooms where polymer materials were used in smaller quantities.

To ensure the safety of using polymer materials, it is accepted that the concentrations of volatile substances released from polymers in residential and public buildings should not exceed their maximum permissible concentrations established for atmospheric air, and the total ratio of the detected concentrations of several substances to their maximum permissible concentrations should not exceed one. For the purpose of preventive sanitary supervision of polymeric materials and products made from them, it is proposed to limit the release of harmful substances V environment either at the manufacturing stage or shortly after their release by the manufacturing plants. Currently, permissible levels of about 100 chemicals released from polymer materials have been substantiated.

In modern construction, there is an increasingly clear tendency towards the chemicalization of technological processes and the use of various substances as mixtures, primarily concrete and reinforced concrete. From a hygienic point of view, it is important to take into account the adverse effects of chemical additives in building materials due to the release of toxic substances.

No less powerful internal sources of indoor environmental pollution are human waste products - anthropotoxins. It has been established that in the process of life, a person releases approximately 400 chemical compounds.

Studies have shown that the air environment of unventilated rooms deteriorates in proportion to the number of people and the time they spend in the room. Chemical analysis of indoor air made it possible to identify a number of toxic substances in them, the distribution of which by hazard class is as follows: dimethylamine, hydrogen sulfide, nitrogen dioxide, ethylene oxide, benzene (second hazard class - highly hazardous substances); acetic acid, phenol, methylstyrene, toluene, methanol, vinyl acetate (third hazard class - low-hazard substances). A fifth of the identified anthropotoxins are classified as highly hazardous substances. It was found that in an unventilated room the concentrations of dimethylamine and hydrogen sulfide exceeded the maximum permissible concentration for atmospheric air. The concentrations of substances such as carbon dioxide, carbon monoxide, and ammonia exceeded or were at their level. The remaining substances, although they constituted tenths or smaller fractions of the maximum permissible concentration, taken together indicated an unfavorable air environment, since even a two to four hour stay in these conditions negatively affected the mental performance of the subjects.

A study of the air environment of gasified premises showed that during an hour-long combustion of gas in the indoor air, the concentration of substances was (mg/m 3): carbon monoxide - on average 15, formaldehyde - 0.037, nitrogen oxide - 0.62, nitrogen dioxide - 0.44, benzene - 0.07. The air temperature in the room during gas combustion increased by 3-6 °C, humidity increased by 10-15%. Moreover, high concentrations of chemical compounds were observed not only in the kitchen, but also in the living areas of the apartment. After shutdown gas appliances the content of carbon monoxide and other chemicals in the air decreased, but sometimes did not return to the original values ​​even after 1.5-2.5 hours.

A study of the effect of household gas combustion products on human external respiration revealed an increase in the load on the respiratory system and a change functional state central nervous system.

One of the most common sources of air pollution closed premises is smoking. At spectrometric analysis 186 chemical compounds were detected in air polluted by tobacco smoke. In insufficiently ventilated areas, air pollution from smoking products can reach 60-90%.

When studying the effects of tobacco smoke components on non-smokers (passive smoking), the subjects observed irritation of the mucous membranes of the eyes, an increase in the content of carboxyhemoglobin in the blood, an increase in heart rate, an increase in the level of blood pressure. Thus, main sources of pollution The air environment of the room can be divided into four groups:

The significance of internal sources of pollution in different types of buildings varies. In administrative buildings, the level of total pollution most closely correlates with the saturation of premises with polymer materials (R = 0.75); in indoor sports facilities, the level of chemical pollution most closely correlates with the number of people in them (R = 0.75). For residential buildings, the closeness of the correlation between the level of chemical pollution both with the saturation of premises with polymer materials and with the number of people in the premises is approximately the same.

Chemical pollution the air environment of residential and public buildings under certain conditions (poor ventilation, excessive saturation of premises with polymer materials, large crowds of people, etc.) can reach a level that affects Negative influence on general state human body.

In recent years, according to WHO, the number of reports of so-called sick building syndrome has increased significantly. The described symptoms of deteriorating health of people living or working in such buildings are very diverse, but they also have a number of common features, namely: headaches, mental fatigue, increased frequency of airborne infections and colds, irritation of the mucous membranes of the eyes, nose, pharynx, feeling of dry mucous membranes and skin, nausea, dizziness.

First category - temporarily "sick" buildings- includes newly built or recently reconstructed buildings, in which the intensity of the manifestation of these symptoms weakens over time and in most cases, after about six months they disappear completely. A decrease in the severity of symptoms may be due to the patterns of emission of volatile components contained in building materials, paints, etc.

In buildings of the second category - constantly "sick" The described symptoms have been observed for many years, and even large-scale health measures may not be effective. An explanation for this situation is, as a rule, difficult to find, despite a thorough study of the composition of the air, the work ventilation system and building design features.

It should be noted that it is not always possible to detect a direct relationship between the state of the indoor air environment and the state of public health.

However, ensuring an optimal air environment in residential and public buildings is an important hygienic and engineering problem. The leading link in solving this problem is the air exchange of rooms, which provides the required air parameters. When designing air conditioning systems in residential and public buildings, the required air supply rate is calculated in a volume sufficient to assimilate human heat and moisture, exhaled carbon dioxide, and in rooms intended for smoking, the need to remove tobacco smoke is also taken into account.

In addition to regulating the amount of supply air and its chemical composition, the electrical characteristics of the air environment are of known importance for ensuring air comfort in an enclosed space. The latter is determined by the ionic regime of the premises, i.e., the level of positive and negative air ionization. Both insufficient and excessive air ionization have a negative effect on the body.

Living in areas with a content of negative air ions of the order of 1000-2000 per ml of air has a beneficial effect on the health of the population.

The presence of people in rooms causes a decrease in the content of light air ions. In this case, the ionization of air changes more intensely, the more people there are in the room and the smaller its area.

A decrease in the number of light ions is associated with the loss of air's refreshing properties, with its lower physiological and chemical activity, which has an adverse effect on the human body and causes complaints of stuffiness and “lack of oxygen.” Therefore, the processes of deionization and artificial ionization of indoor air are of particular interest, which, naturally, must have hygienic regulation.

It must be emphasized that artificial ionization of indoor air without sufficient air supply in conditions of high humidity and dustiness of the air leads to an inevitable increase in the number of heavy ions. In addition, in the case of ionization of dusty air, the percentage of dust retention in the respiratory tract increases sharply (dust carrying electrical charges is retained in the human respiratory tract in much greater quantities than neutral dust).

Consequently, artificial air ionization is not a universal panacea for improving the health of indoor air. Without improving all hygienic parameters of the air environment, artificial ionization not only does not improve human living conditions, but, on the contrary, can have a negative effect.

The optimal total concentrations of light ions are levels of the order of 3 x 10, and the minimum required is 5 x 10 in 1 cm 3. These recommendations formed the basis of the sanitary and hygienic standards in force in the Russian Federation for permissible levels of air ionization in industrial and public premises (Table 6.1).

Physico-chemical properties of natural gas

Natural gas colorless, odorless and tasteless, non-toxic.

Gas density at t = 0°C, P = 760 mm Hg. Art.: methane - 0.72 kg/m 3, air -1.29 kg/m 3.

The auto-ignition temperature of methane is 545 – 650°C. This means that any mixture of natural gas and air heated to this temperature will ignite without an ignition source and will burn.

Methane combustion temperature is 2100°C in furnaces 1800°C.

Heat of combustion of methane: Qn = 8500 kcal/m3, Qv = 9500 kcal/m3.

Explosiveness. There are:

– the lower explosive limit is the lowest gas content in the air at which an explosion occurs; for methane it is 5%.

With a lower gas content in the air, there will be no explosion due to lack of gas. When a third-party energy source is introduced, there is a popping sound.

– the upper explosive limit is the highest gas content in the air at which an explosion occurs; for methane it is 15%.

With a higher gas content in the air, there will be no explosion due to lack of air. When a third-party energy source is introduced, a fire occurs.

For a gas explosion, in addition to keeping it in the air within the limits of its explosiveness, a third-party source of energy (spark, flame, etc.) is required.

When a gas explodes in a closed volume (room, furnace, tank, etc.), there is more destruction than outdoors.

When gas is burned with underburning, i.e. with a lack of oxygen, carbon monoxide (CO) is formed in the combustion products, or carbon monoxide, which is a highly toxic gas.

The flame propagation speed is the speed at which the flame front moves relative to the fresh mixture jet.

The approximate speed of methane flame propagation is 0.67 m/s. It depends on the composition, temperature, pressure of the mixture, the ratio of gas and air in the mixture, the diameter of the flame front, the nature of the movement of the mixture (laminar or turbulent) and determines the stability of combustion.

Gas odorization- This is the addition of a strong-smelling substance (odorant) to gas to give the gas an odor before delivery to consumers.

Requirements for odorants:

– pungent specific odor;

– must not interfere with combustion;

– must not dissolve in water;

– must be harmless to humans and equipment.

Ethyl mercaptan (C 2 H 5 SH) is used as an odorant; it is added to methane - 16 g per 1000 m 3, the rate doubles in winter.

A person should smell the odorant in the air when the gas content in the air is 20% of the lower explosive limit for methane - 1% by volume.

This chemical process combinations of flammable components (hydrogen and carbon) with oxygen contained in the air. Occurs with the release of heat and light.

When carbon is burned, carbon dioxide (C0 2) is formed, and hydrogen produces water vapor (H 2 0).

Combustion stages: gas and air supply, formation gas-air mixture, ignition of the mixture, its combustion, removal of combustion products.

Theoretically, when all the gas burns and all the required amount of air takes part in the combustion, the combustion reaction of 1 m 3 of gas is:

CH 4 + 20 2 = CO 2 + 2H 2 O + 8500 kcal/m 3.

To burn 1 m 3 of methane, 9.52 m 3 of air is required.

Almost not all of the combustion air will take part in combustion.

Therefore, in addition to carbon dioxide (C0 2) and water vapor (H 2 0), combustion products will contain:

– carbon monoxide, or carbon monoxide (CO), if released into a room can cause poisoning service personnel;

– atomic carbon, or soot (C), deposited in flues and furnaces, impairs draft, and heat transfer on heating surfaces.

– unburned gas and hydrogen accumulate in fireboxes and flues and form an explosive mixture.

When there is a lack of air, incomplete combustion of the fuel occurs - the combustion process occurs with underburning. Underburning also occurs when the gas is poorly mixed with air and the temperature in the combustion zone is low.

For complete combustion gas, the combustion air is supplied in sufficient quantity, the air and gas must be well mixed, and a high temperature is required in the combustion zone.

For complete combustion of gas, air is supplied in greater quantities than theoretically required, i.e. in excess, not all of the air will take part in combustion. Part of the heat will be used to heat this excess air and will be released into the atmosphere.

Excess air coefficient α is a number showing how many times the actual combustion flow rate is greater than it is theoretically required:

α = V d / V t

where V d - actual air flow, m 3;

V t - theoretically required air, m 3.

α = 1.05 – 1.2.

Gas combustion methods

Combustion air can be:

– primary – fed into the burner, mixed with gas, and the gas-air mixture is used for combustion;

– secondary – enters the combustion zone.

Gas combustion methods:

1. Diffusion method - gas and combustion air are supplied separately and mixed in the combustion zone, all air is secondary. The flame is long and requires a large combustion space.

2. Mixed method - part of the air is supplied inside the burner, mixed with gas (primary air), part of the air is supplied to the combustion zone (secondary). The flame is shorter than with the diffusion method.

3. Kinetic method - all air is mixed with gas inside the burner, i.e. all air is primary. The flame is short and a small combustion space is required.

Gas burner devices

Gas burners are devices that supply gas and air to the combustion front, form a gas-air mixture, stabilize the combustion front, and ensure the required intensity of the combustion process.

A burner equipped with an additional device (tunnel, air distribution device, etc.) is called a gas burner device.

Burner requirements:

1) must be factory-made and pass state tests;

2) must ensure complete gas combustion in all operating modes with minimal excess air and minimal emissions of harmful substances into the atmosphere;

3) be able to use automatic control and safety systems, as well as measure gas and air parameters in front of the burner;

4) must have a simple design, be accessible for repair and inspection;

5) must operate stably within the operating regulation limits, if necessary, have stabilizers to prevent flame separation and breakthrough;

6) for operating burners, the noise level should not exceed 85 dB, and the surface temperature should not exceed 45 ° C.

Gas burner parameters

1) thermal power of the burner N g - the amount of heat released during gas combustion in 1 hour;

2) the lowest limit of stable operation of the burner N n. .P. . – the lowest power at which the burner operates stably without flame separation or flashover;

3) minimum power N min – power of the lowest limit, increased by 10%;

4) upper limit of stable operation of the burner N in. .P. . - the highest power at which the burner operates stably without flame separation or flashover;

5) maximum power N max – upper limit power, reduced by 10%;

6) rated power N nom - the highest power with which the burner operates for a long time with the highest efficiency;

7) range of operating regulation – power values ​​from N min to N nom;

8) operating regulation coefficient - the ratio of rated power to minimum.

Classification of gas burners:

1) according to the method of supplying combustion air:

– blowless – air enters the furnace due to rarefaction in it;

– injection – air is sucked into the burner due to the energy of the gas stream;

– blowing – air is supplied to the burner or furnace using a fan;

2) according to the degree of preparation of the combustible mixture:

– without preliminary mixing of gas with air;

– with complete pre-mixing;

– with incomplete or partial pre-mixing;

3) by the speed of combustion products flow (low – up to 20 m/s, medium – 20-70 m/s, high – more than 70 m/s);

4) by gas pressure in front of the burners:

– low up to 0.005 MPa (up to 500 mm water column);

– average from 0.005 MPa to 0.3 MPa (from 500 mm water column to 3 kgf/cm 2);

– high more than 0.3 MPa (more than 3 kgf/cm 2);

5) according to the degree of automation of burner control - manually controlled, semi-automatic, automatic.

According to the method of air supply, burners can be:

1) Diffusion. All air comes to the torch from the surrounding space. Gas is supplied to the burner without primary air and, leaving the manifold, is mixed with air outside it.

The simplest burner in design is usually a pipe with holes drilled in one or two rows.

A variety is a hearth burner. Consists of a gas manifold made of steel pipe, plugged at one end. Holes are drilled in the pipe in two rows. The collector is installed in the slots, made of refractory bricks resting on the grate. Gas exits through holes in the manifold into the slot. Air enters the same slot through the grate due to vacuum in the firebox or with the help of a fan. During operation, the refractory lining of the slot heats up, ensuring stabilization of the flame in all operating modes.

Advantages of the burner: simplicity of design, reliable operation (flame leakage is impossible), noiselessness, good regulation.

Flaws: low power, uneconomical, high flame.

2) Injection burners:

A) low pressure or atmospheric (refer to burners with partial premixing). The gas stream comes out of the nozzle at high speed and, due to its energy, captures air into the confuser, dragging it inside the burner. The mixing of gas with air occurs in a mixer consisting of a neck, a diffuser and a fire nozzle. The vacuum created by the injector increases with increasing gas pressure, and the amount of primary air sucked in changes. The amount of primary air can be changed using an adjusting washer. By changing the distance between the washer and the confuser, the air supply is adjusted.

To ensure complete combustion of the fuel, part of the air is supplied due to rarefaction in the firebox (secondary air). Its flow rate is regulated by changing the vacuum.

They have the property of self-regulation: with increasing load, the gas pressure increases, which injects an increased amount of air into the burner. As the load decreases, the amount of air decreases.

Burners are used to a limited extent on high-capacity equipment (more than 100 kW). This is due to the fact that the burner manifold is located directly in the firebox. During operation it heats up to high temperatures and quickly fails. They have a high excess air ratio, which leads to uneconomical gas combustion.

b) Medium pressure. By increasing the gas pressure, all the air required for complete combustion of the gas is injected. All air is primary. They operate at gas pressure from 0.005 MPa to 0.3 MPa. Refer to burners for complete pre-mixing of gas with air. As a result of good mixing of gas and air, they operate with a low excess air ratio (1.05-1.1). Kazantsev burner. Consists of a primary air regulator, nozzle, mixer, nozzle and plate stabilizer. Coming out of the nozzle, the gas has enough energy to inject all the air needed for combustion. In the mixer, gas and air are completely mixed. The primary air regulator simultaneously dampens the noise that occurs due to the high speed of the gas-air mixture. Advantages:

– simplicity of design;

– stable operation when the load changes;

– lack of air supply under pressure (no fan, electric motor, air ducts);

– possibility of self-regulation (maintaining a constant gas-air ratio).

Flaws:

– large dimensions of burners along the length, especially burners with increased productivity;

– high level noise.

3) Burners with forced submission air. The formation of the gas-air mixture begins in the burner and ends in the furnace. Air is supplied by a fan. Gas and air are supplied through separate pipes. They operate on low and medium pressure gas. For better mixing, the gas flow is directed through the holes at an angle to the air flow.

To improve mixing, the air flow is given a rotational movement using swirlers with a constant or adjustable blade angle.

Gas vortex burner (GGV) - gas from the distribution manifold exits through holes drilled in one row and at an angle of 90 0 enters the air flow swirled using a blade swirler. The blades are welded at an angle of 45 0 to outer surface gas manifold. Inside the gas manifold there is a pipe to monitor the combustion process. When working with fuel oil, a steam-mechanical nozzle is installed in it.

Burners designed to burn several types of fuel are called combined burners.

Advantages of burners: high thermal power, wide range of operating regulation, the ability to regulate the excess air ratio, the ability to preheat gas and air.

Disadvantages of burners: sufficient complexity of design; flame separation and breakthrough are possible, which makes it necessary to use combustion stabilizers (ceramic tunnel, pilot torch, etc.).

Burner accidents

The amount of air in the gas-air mixture is the most important factor influencing the speed of flame propagation. In mixtures in which the gas content exceeds the upper limit of its ignition, the flame does not propagate at all. With an increase in the amount of air in the mixture, the speed of flame propagation increases, reaching its greatest value when the air content is about 90% of its theoretical amount required for complete combustion of the gas. As the air flow to the burner increases, a mixture that is leaner in gas is created, which can burn faster and cause the flame to leak into the burner. Therefore, if it is necessary to increase the load, first increase the gas supply and then the air. If it is necessary to reduce the load, do the opposite - first reduce the air supply, and then the gas. At the moment of starting the burners, no air should enter them and the gas is ignited in a diffusion mode due to the air entering the firebox, followed by the transition to air supply to the burner

1. Flame separation - movement of the torch zone from the burner outlets in the direction of fuel combustion. Occurs when the speed of the gas-air mixture becomes greater than the speed of flame propagation. The flame becomes unstable and may go out. Gas continues to flow through the extinguished burner, which leads to the formation of an explosive mixture in the firebox.

Separation occurs when: an increase in gas pressure above the permissible level, a sharp increase in the supply of primary air, an increase in vacuum in the furnace, operation of the burner in extreme modes relative to those indicated in the passport.

2. Flame breakthrough - movement of the torch zone towards the combustible mixture. Happens only in burners with pre-mixing of gas and air. Occurs when the speed of the gas-air mixture becomes less than the speed of flame propagation. The flame jumps inside the burner, where it continues to burn, causing deformation of the burner due to overheating. If there is a breakthrough, there may be a small pop, the flame will go out, and gas contamination of the firebox and flue ducts will occur through the inoperative burner.

Surge occurs when: the gas pressure in front of the burner decreases below the permissible level; igniting the burner when supplying primary air; large gas supply at low air pressure, reduction in burner productivity by pre-mixing gas and air below the values ​​​​specified in the passport. Not possible with the diffusion method of gas combustion.

Actions of personnel in the event of a burner accident:

– turn off the burner,

– ventilate the firebox,

- to figure out cause of the accident,

- make a journal entry,

Gas combustion is a combination of the following processes:

mixing of flammable gas with air,

· heating the mixture,

thermal decomposition of flammable components,

· ignition and chemical combination of flammable components with atmospheric oxygen, accompanied by the formation of a torch and intense heat release.

Methane combustion occurs according to the reaction:

CH 4 + 2O 2 = CO 2 + 2H 2 O

Conditions necessary for gas combustion:

· ensuring the required ratio of combustible gas and air,

· heating to ignition temperature.

If the gas-air mixture contains less than the lower flammable limit, it will not burn.

If there is more gas in the gas-air mixture than the upper flammability limit, then it will not burn completely.

Composition of products of complete combustion of gas:

· CO 2 – carbon dioxide

· H 2 O – water vapor

* N 2 – nitrogen (it does not react with oxygen during combustion)

Composition of products of incomplete combustion of gas:

· CO – carbon monoxide

· C – soot.

To burn 1 m 3 of natural gas, 9.5 m 3 of air is required. In practice, air consumption is always higher.

Attitude actual consumption air to theoretically required flow is called the excess air coefficient: α = L/L t.,

Where: L - actual consumption;

L t is the theoretically required flow rate.

The excess air coefficient is always greater than one. For natural gas it is 1.05 – 1.2.

2. Purpose, design and main characteristics of instantaneous water heaters.

Instantaneous gas water heaters. Designed to heat water to a certain temperature when drawing water. Instantaneous water heaters are divided according to the thermal power load: 33600, 75600, 105000 kJ, according to the degree of automation - into the highest and first classes. Efficiency water heaters 80%, oxide content no more than 0.05%, temperature of combustion products behind the draft breaker no less than 180 0 C. The principle is based on heating water during water withdrawal.

The main components of instantaneous water heaters are: gas burner device, heat exchanger, automation system and gas outlet. Low pressure gas is supplied to the injection burner. Combustion products pass through a heat exchanger and are discharged into the chimney. The heat of combustion is transferred to the water flowing through the heat exchanger. To cool the fire chamber, a coil is used, through which water circulates, passing through the heater. Gas instantaneous water heaters are equipped with gas exhaust devices and draft interrupters, which, in the event of a short-term loss of draft, prevent the flame of the gas burner from going out. There is a smoke outlet pipe for connection to the chimney.

Gas instantaneous water heater–HSV. On the front wall of the casing there are: a gas valve control handle, a button for turning on the solenoid valve and an observation window for observing the flame of the ignition and main burner. At the top of the device there is a smoke exhaust device, at the bottom there are pipes for connecting the device to the gas and water systems. Gas enters the solenoid valve, the gas block valve of the water-gas burner unit carries out serial connection pilot burner and gas supply to the main burner.

Blocking the flow of gas to the main burner, when the igniter is required to operate, is carried out by an electromagnetic valve powered by a thermocouple. Blocking the gas supply to the main burner, depending on the presence of water supply, is carried out by a valve driven through a rod from the membrane of the water block tap.

General information. Another important source of internal pollution, a strong sensitizing factor for humans, is natural gas and its combustion products. Gas is a multicomponent system consisting of dozens various connections, including those specially added (Table.

There is direct evidence that the use of appliances that burn natural gas (gas stoves and boilers) has an adverse effect on human health. In addition, individuals with increased sensitivity to environmental factors react inadequately to the components of natural gas and its combustion products.

Natural gas in the home is a source of many different pollutants. These include compounds that are directly present in the gas (odorants, gaseous hydrocarbons, toxic organometallic complexes and radioactive gas radon), products of incomplete combustion (carbon monoxide, nitrogen dioxide, aerosolized organic particles, polycyclic aromatic hydrocarbons and small amounts of volatile organic compounds). All of these components can affect the human body either on their own or in combination with each other (synergy effect).

Table 12.3

Composition of gaseous fuel

Odorants. Odorants are sulfur-containing organic aromatic compounds (mercaptans, thioethers and thio-aromatic compounds). Added to natural gas to detect leaks. Although these compounds are present in very small, subthreshold concentrations that are not considered toxic to most individuals, their odor can cause nausea and headaches in healthy individuals.

Clinical experience and epidemiological data indicate that chemically sensitive people react inappropriately to chemical compounds present even at subthreshold concentrations. Individuals with asthma often identify odor as a promoter (trigger) of asthmatic attacks.

Odorants include, for example, methanethiol. Methanethiol, also known as methyl mercaptan (mercaptomethane, thiomethyl alcohol), is a gaseous compound that is commonly used as an aromatic additive to natural gas. Unpleasant smell is experienced by most people at a concentration of 1 part in 140 ppm, however this compound can be detected at significantly lower concentrations by highly sensitive individuals.

Toxicological studies in animals have shown that 0.16% methanethiol, 3.3% ethanethiol, or 9.6% dimethyl sulfide are capable of inducing coma in 50% of rats exposed to these compounds for 15 minutes.

Another mercaptan, also used as an aromatic additive to natural gas, is mercaptoethanol (C2H6OS) also known as 2-thioethanol, ethyl mercaptan. Strong irritant to eyes and skin, capable of causing toxic effects through the skin. It is flammable and decomposes when heated to form highly toxic SOx vapors.

Mercaptans, being indoor air pollutants, contain sulfur and are capable of capturing elemental mercury. In high concentrations, mercaptans can cause impaired peripheral circulation and increased heart rate, and can stimulate loss of consciousness, the development of cyanosis, or even death.

Aerosols. The combustion of natural gas produces small organic particles (aerosols), including carcinogenic aromatic hydrocarbons, as well as some volatile organic compounds. DOS are suspected sensitizing agents that, together with other components, can induce the “sick building” syndrome, as well as multiple chemical sensitivity (MCS).

DOS also includes formaldehyde, which is formed in small quantities during gas combustion. The use of gas appliances in a home occupied by sensitive individuals increases exposure to these irritants, subsequently increasing symptoms of illness and also promoting further sensitization.

Aerosols generated during the combustion of natural gas can become adsorption sites for a variety of chemical compounds present in the air. Thus, air pollutants can concentrate in microvolumes and react with each other, especially when metals act as reaction catalysts. The smaller the particle, the higher the concentration activity of this process.

Moreover, water vapor generated during the combustion of natural gas is a transport link for aerosol particles and pollutants as they are transferred to the pulmonary alveoli.

The combustion of natural gas also produces aerosols containing polycyclic aromatic hydrocarbons. They have adverse effects on the respiratory system and are known carcinogens. In addition, hydrocarbons can lead to chronic intoxication in susceptible people.

The formation of benzene, toluene, ethylbenzene and xylene during the combustion of natural gas is also unfavorable for human health. Benzene is known to be carcinogenic at doses well below threshold levels. Exposure to benzene is correlated with an increased risk of cancer, especially leukemia. The sensitizing effects of benzene are not known.

Organometallic compounds. Some components of natural gas may contain high concentrations of toxic heavy metals, including lead, copper, mercury, silver and arsenic. In all likelihood, these metals are present in natural gas in the form of organometallic complexes such as trimethylarsenite (CH3)3As. The association of these toxic metals with the organic matrix makes them lipid soluble. This leads to high levels of absorption and a tendency to bioaccumulate in human adipose tissue. The high toxicity of tetramethylplumbite (CH3)4Pb and dimethylmercury (CH3)2Hg suggests an impact on human health, since the methylated compounds of these metals are more toxic than the metals themselves. These compounds pose a particular danger during lactation in women, since in this case lipids migrate from the body’s fat depots.

Dimethylmercury (CH3)2Hg is a particularly dangerous organometallic compound due to its high lipophilicity. Methylmercury can be incorporated into the body through inhalation and also through the skin. The absorption of this compound in the gastrointestinal tract is almost 100%. Mercury has a pronounced neurotoxic effect and the ability to influence human reproductive function. Toxicology does not have data on safe levels mercury for living organisms.

Organic arsenic compounds are also very toxic, especially when they are destroyed metabolically (metabolic activation), resulting in the formation of highly toxic inorganic forms.

Natural gas combustion products. Nitrogen dioxide is able to act on the pulmonary system, which facilitates the development allergic reactions to other substances, reduces lung function, susceptibility to infectious lung diseases, potentiates bronchial asthma and other respiratory diseases. This is especially pronounced in children.

There is evidence that NO2 produced by burning natural gas can induce:

• inflammation of the pulmonary system and decreased vital function of the lungs;
• increased risk of asthma-like symptoms, including wheezing, shortness of breath and attacks. This is especially common in women who cook on gas stoves, as well as in children;
• decreased resistance to bacterial lung diseases due to a decrease in the immunological mechanisms of lung defense;
• causing adverse effects in general on the immune system of humans and animals;
• influence as an adjuvant on the development of allergic reactions to other components;
• increased sensitivity and increased allergic response to adverse allergens.

Natural gas combustion products contain a fairly high concentration of hydrogen sulfide (H2S), which pollutes the environment. It is poisonous in concentrations lower than 50.ppm, and in concentrations of 0.1-0.2% is fatal even with short exposure. Since the body has a mechanism to detoxify this compound, the toxicity of hydrogen sulfide is related more to its exposure concentration than to the duration of exposure.

Although hydrogen sulfide has a strong odor, continuous low concentration exposure leads to loss of the sense of smell. This makes it possible for toxic effects to occur in people who may be unknowingly exposed to dangerous levels of this gas. Minor concentrations of it in the air of residential premises lead to irritation of the eyes and nasopharynx. Moderate levels cause headache, dizziness, as well as coughing and difficulty breathing. High levels lead to shock, convulsions, coma, which ends in death. Survivors of acute hydrogen sulfide toxicity experience neurological dysfunction such as amnesia, tremors, imbalance, and sometimes more severe brain damage.

The acute toxicity of relatively high concentrations of hydrogen sulfide is well known, but unfortunately little information is available on chronic LOW-DOSE exposure to this component.

Radon. Radon (222Rn) is also present in natural gas and can be carried through pipelines to gas stoves, which become sources of pollution. Since radon decays to lead (210Pb has a half-life of 3.8 days), it creates a thin layer of radioactive lead (average 0.01 cm thick) that covers internal surfaces pipes and equipment. The formation of a layer of radioactive lead increases the background value of radioactivity by several thousand decays per minute (over an area of ​​100 cm2). Removing it is very difficult and requires replacing the pipes.

It should be borne in mind that simply turning off the gas equipment is not enough to remove the toxic effects and bring relief to chemically sensitive patients. Gas equipment must be completely removed from the room, since even a gas stove that is not working continues to release aromatic compounds that it has absorbed over the years of use.

The cumulative effects of natural gas, the influence of aromatic compounds, and combustion products on human health are not precisely known. It is hypothesized that effects from multiple compounds may be multiplying, and the response from exposure to multiple pollutants may be greater than the sum of the individual effects.

In summary, the characteristics of natural gas that cause concern for human and animal health are:

• flammable and explosive nature;
• asphyxial properties;
• pollution of indoor air by combustion products;
• presence of radioactive elements (radon);
• content of highly toxic compounds in combustion products;
• the presence of trace amounts of toxic metals;
• toxic aromatic compounds added to natural gas (especially for people with multiple chemical sensitivities);
• the ability of gas components to sensitize.

Composition and properties of natural gas. Natural gas (combustible natural gas; GGP) - A gaseous mixture consisting of methane and heavier hydrocarbons, nitrogen, carbon dioxide, water vapor, sulfur-containing compounds, inert gases . Methane is the main component of HGP. HGP usually also contains trace amounts of other components (Fig. 1).

1. Combustible components include hydrocarbons:

a) methane (CH 4) is the main component of natural gas, up to 98% by volume (the remaining components are present in small quantities or absent). Colorless, odorless and tasteless, non-toxic, explosive, lighter than air;

b) heavy (saturated) hydrocarbons [ethane (C 2 H 6), propane (C 3 H 8), butane (C 4 H 10), etc.] - colorless, odorless and tasteless, non-toxic, explosive, heavier than air.

2. Non-combustible components (ballast) :

a) nitrogen (N 2) - component air, without color, smell and taste; inert gas, because it does not interact with oxygen;

b) oxygen (O 2) - a component of air; colorless, odorless and tasteless; oxidizing agent.

c) carbon dioxide (carbon dioxide CO 2) - colorless with a slightly sour taste. When contained in the air more than 10%, it is toxic, heavier than air;

Air . Dry atmospheric air is a multicomponent gas mixture consisting of (vol. %): nitrogen N 2 - 78%, oxygen O 2 - 21%, inert gases (argon, neon, krypton, etc.) - 0.94% and carbon dioxide – 0.03%.

Fig.2. Air composition.

The air also contains water vapor and random impurities - ammonia, sulfur dioxide, dust, microorganisms, etc. ( rice. 2). The gases that make up the air are distributed evenly in it and each of them retains its properties in the mixture.

3. Harmful components :

a) hydrogen sulfide (H 2 S) - colorless, with the smell of rotten eggs, toxic, flammable, heavier than air.

b) hydrocyanic acid (HCN) is a colorless light liquid, in a gas it has a gaseous state. Toxic, causes corrosion of metal.

4. Mechanical impurities (content depends on gas transportation conditions):

a) resins and dust - when mixed, they can form blockages in gas pipelines;

b) water - at low temperatures freezes to form ice jams, which leads to freezing of the reducing devices.

GGPBy toxicological characteristics belong to substances of the ΙV-th hazard class according to GOST 12.1.007. These are gaseous, low-toxic, fire and explosive products.

Density: atmospheric air density under normal conditions - 1.29 kg/m3, and methane - 0.72 kg/m 3 Therefore, methane is lighter than air.

GOST 5542-2014 requirements for GGP indicators:

1) mass concentration of hydrogen sulfide- no more than 0.02 g/m 3 ;

2) mass concentration of mercaptan sulfur- no more than 0.036 g/m 3 ;

3) mole fraction of oxygen- no more than 0.050%;

4) permissible content of mechanical impurities- no more than 0.001 g/m 3;

5) mole fraction of carbon dioxide in natural gas, no more than 2.5%.

6) Net calorific value GGP under standard combustion conditions according to GOST 5542-14 - 7600 kcal/m 3 ;

8) gas odor intensity for for municipal purposes with a volume fraction of 1% in the air - at least 3 points, and for gas industrial purposes this indicator is established in agreement with the consumer.

Sales expense unit GGP - 1 m 3 of gas at a pressure of 760 mm Hg. Art. and temperature 20 o C;

Auto-ignition temperature– the lowest temperature of a heated surface, which, under given conditions, ignites flammable substances in the form of a gas or steam-air mixture. For methane it is 537 °C. Combustion temperature (maximum temperature in the combustion zone): methane - 2043 °C.

Specific heat methane combustion: lowest - QH = 8500 kcal/m3, highest - Qв - 9500 kcal/m3. For the purpose of comparing fuel types, the concept standard fuel (ce) , in the Russian Federation per unit the calorific value of 1 kg was taken coal, equal 29.3 MJ or 7000 kcal/kg.

Conditions for measuring gas flow are::

· normal conditions(n. at): standard physical conditions, with which the properties of substances are usually correlated. Normal conditions are defined by IUPAC (International Union of Practical and Applied Chemistry) as follows: Atmosphere pressure 101325 Pa = 760 mmHg st..Air temperature 273.15 K = 0°C .Methane density at Well.- 0.72 kg/m 3,

· standard conditions(With. at) volume with mutual ( commercial) settlements with consumers - GOST 2939-63: temperature 20°C, pressure 760 mm Hg. (101325 N/m), humidity is zero. (By GOST 8.615-2013 normal conditions are referred to as "standard conditions"). Methane density at s.u.- 0.717 kg/m 3.

Flame propagation speed (burning speed)– speed of movement of the flame front relative to the fresh jet of combustible mixture in a given direction. Approximate flame propagation speed: propane - 0.83 m/s, butane - 0.82 m/s, methane - 0.67 m/s, hydrogen - 4.83 m/s, depends on the composition, temperature, pressure of the mixture, the ratio of gas and air in the mixture, the diameter of the flame front, the nature of the movement of the mixture (laminar or turbulent) and determines the stability of combustion.

To the disadvantages (hazardous properties) GGP include: explosiveness (flammability); intense combustion; rapid spread in space; inability to determine location; suffocating effect, with a lack of oxygen for breathing .

Explosiveness (flammability) . Distinguish:

A) lower flammability limit ( NPV) – the lowest gas content in the air at which the gas ignites (methane – 4.4%) . With a lower gas content in the air, there will be no ignition due to a lack of gas; (Fig. 3)

b) upper flammability limit ( ERW) – the highest gas content in the air at which the ignition process occurs ( methane – 17%) . With a higher gas content in the air, ignition will not occur due to lack of air. (Fig. 3)

IN FNP NPV And ERW called lower and upper concentration limits of flame propagation ( NCPRP And VKPRP) .

At increasing gas pressure the range between the upper and lower limits of gas pressure decreases (Fig. 4).

For a gas explosion (methane) except its content in the air within the limits of flammability necessary external energy source (spark, flame, etc.) . In case of gas explosion in a closed volume (room, firebox, tank, etc.), more destruction than an explosion in the open air (rice. 5).

Maximum permissible concentrations ( MPC) harmful substances GGP in the air of the working area are established in GOST 12.1.005.

Maximum one-time MPC in the air of the working area (in terms of carbon) is 300 mg/m3.

Dangerous concentration GGP (volume fraction of gas in air) is the concentration equal to 20% of the lower flammability limit of the gas.

Toxicity - the ability to poison the human body. Hydrocarbon gases do not have a strong toxicological effect on the human body, but their inhalation causes dizziness in a person, and their significant content in the inhaled air. When oxygen decreases to 16% or less, can lead to suffocation.

At burning gas with insufficient oxygen, i.e. with underburning, the combustion products form carbon monoxide (CO), or carbon monoxide, which is a highly toxic gas.

Gas odorization - adding a strong-smelling substance (odorant) to the gas to give it an odor GGP before delivery to consumers in urban networks. At use for odorization of ethyl mercaptan (C 2 H 5 S H - according to the degree of impact on the body belongs to the ΙΙ class of toxicological hazard according to GOST 12.1.007-76 ), it is added 16 g per 1000m 3 . The intensity of the odor of odorized HGP with a volume fraction of 1% in the air must be at least 3 points according to GOST 22387.5.

Non-odorized gas can be supplied to industrial enterprises, because natural gas odor intensity for industrial enterprises consuming gas from main gas pipelines is established by agreement with the consumer.

Combustion of gases. The combustion chamber of a boiler (furnace), in which gaseous (liquid) fuel is burned in a torch, corresponds to the concept of a “chamber combustion chamber of a stationary boiler.”

Combustion of hydrocarbon gases – chemical combination of flammable gas components (carbon C and hydrogen H) with air oxygen O2 (oxidation) with the release of heat and light: CH 4 +2O 2 =CO 2 +2H 2 O .

With complete combustion carbon produces carbon dioxide (CO 2), and water kind - water vapor (H 2 O) .

In theory To burn 1 m 3 of methane, 2 m 3 of oxygen is required, which is contained in 9.52 m 3 of air (Fig. 6). If There is not enough combustion air supplied , then for some molecules of combustible components there will not be enough oxygen molecules and in combustion products, in addition to carbon dioxide (CO 2), nitrogen (N 2) and water vapor (H 2 O), products incomplete combustion of gas :

-carbon monoxide (CO), which, if released into the premises, can cause poisoning of service personnel;

- soot (C) , which, deposited on heating surfaces impairs heat transfer;

- unburned methane and hydrogen , which can accumulate in fireboxes and flues (chimneys), forming an explosive mixture. When there is a lack of air, it happens incomplete combustion of fuel or, as they say, the combustion process occurs with underburning. Underburning can also occur when poor mixing of gas with air and low temperature in the combustion zone.

For complete combustion of gas it is necessary: ​​the presence of air in the place of combustion in sufficient quantity and good mixing with gas; high temperature in the combustion zone.

To ensure complete combustion of the gas, air is supplied in greater quantities than theoretically required, i.e. in excess, and not all of the air will take part in combustion. Part of the heat will be used to heat this excess air and will be released into the atmosphere along with the flue gas.

The completeness of combustion is determined visually (there should be a bluish flame with purple ends) or by analyzing the composition of the flue gases.

Theoretical (stoichiometric) combustion air volume is the amount of air required for complete combustion of a unit volume ( 1 m 3 of dry gas or mass of fuel, calculated by chemical composition fuel ).

Valid (actual, necessary) Combustion air volume is the amount of air actually used to burn a unit volume or mass of fuel.

Excess air coefficient for combustion α is the ratio of the actual volume of combustion air to the theoretical one: α = V f / V t >1,

Where: V f - actual volume of supplied air, m 3 ;

V t – theoretical volume of air, m3.

Coefficient excess shows how many times actual air consumption for gas combustion exceeds theoretical depends on the design of the gas burner and furnace: the more perfect they are, the higher the coefficient α less. When the excess air coefficient for boilers is less than 1, it leads to incomplete combustion of gas. Increasing the excess air ratio reduces efficiency. gas-using installation. For a number of furnaces where metal is melted, in order to avoid oxygen corrosion - α < 1 and a combustion chamber for unburnt combustible components is installed behind the firebox.

To regulate traction, guide vanes, gates, rotary valves and electromechanical couplings are used.

Advantages of gaseous fuel compared to solid and liquid– low cost, easier labor for personnel, low amount of harmful impurities in combustion products, improved environmental protection conditions, no need for road and rail transport, good mixing with air (less than α), full automation, high efficiency.

Gas combustion methods. Combustion air can be:

1) primary, is fed inside the burner, where it is mixed with gas (a gas-air mixture is used for combustion).

2) secondary, enters directly into the combustion zone.

The following gas combustion methods are distinguished:

1. Diffusion method- gas and combustion air are supplied separately and mixed in the combustion zone, i.e. all air is secondary. The flame is long and requires a large combustion space. (Fig. 7a).

2. Kinetic method - all the air is mixed with the gas inside the burner, i.e. all air is primary. The flame is short, a small combustion space is required (Fig. 7c).

3. Mixed method - part of the air is supplied inside the burner, where it is mixed with gas (this is primary air), and part of the air is supplied to the combustion zone (secondary). The flame is shorter than with the diffusion method (Fig. 7b).

Removal of combustion products. Vacuum in the furnace and removal of combustion products are produced by traction force overcoming resistance smoke path and arising due to the pressure difference between equal-height columns of external cold air and lighter hot flue gas. In this case, the flue gases move from the firebox into the pipe, and in their place, cold air(Fig. 8).

The traction force depends on: air and flue gas temperatures, height, diameter and wall thickness chimney, barometric (atmospheric) pressure, state of gas ducts (chimneys), air suction, vacuum in the firebox .

Natural draft force - created by the height of the chimney, and artificial, which is a smoke exhauster when there is insufficient natural craving. The draft force is regulated by dampers, guide vanes of smoke exhausters and other devices.

Excess air ratio (α ) depends on the design of the gas burner and furnace: the more perfect they are, the smaller the coefficient and shows how many times the actual air consumption for gas combustion exceeds the theoretical one.

Pressurization - removal of fuel combustion products due to the operation of blower fans .When operating “under pressurization”, a strong, dense combustion chamber (furnace) is required that can withstand the excess pressure created by the fan.

Gas burner devices.Gas-burners- provide supply required quantity gas and air, their mixing and regulation of the combustion process, and equipped with a tunnel, air distribution device, etc., is called a gas burner device.

Burner requirements:

1) burners must meet the requirements of the relevant technical regulations(have a certificate or declaration of conformity) or undergo an industrial safety examination;

2) ensure complete combustion of gas in all operating modes with minimal excess air (except for some burners of gas furnaces) and minimal emissions of harmful substances;

3) be able to use automatic control and safety systems, as well as measure gas and air parameters in front of the burner;

4) must have a simple design, be accessible for repair and inspection;

5) work stably within the operating regulation limits, if necessary, have stabilizers to prevent flame separation and breakthrough;

Gas burner parameters(Fig. 9). According to GOST 17356-89 (Gas, liquid fuel and combined burners. Terms and definitions. Amendment No. 1) :Burner stability limit , at which have not yet arisen extinction, breakdown, separation, flame breakthrough and unacceptable vibrations.

Note. Exist top and bottom limits of sustainable operation.

1) Burner thermal power N g. – the amount of heat generated as a result of combustion of fuel supplied to the burner per unit time, N g =V. Q kcal/h, where V is the hourly gas consumption, m 3 /h; Q n. - heat of combustion of gas, kcal/m3.

2) Burner operation stability limits , at which have not yet arisen extinction, failure, separation, flame breakthrough and unacceptable vibrations . Note. Exist top - N vp . and lower -N n.p. limits of sustainable operation.

3) minimum power N min. - thermal power of the burner, amounting to 1.1 power, corresponding to the lower limit of its stable operation, i.e. low limit power increased by 10%, N min. =1.1N n.p.

4) upper limit of stable operation of the burner N v.p. – the highest stable power, operation without separation or flashover of the flame.

5) maximum burner power N max – thermal power of the burner, amounting to 0.9 power, corresponding to the upper limit of its stable operation, i.e. upper limit power reduced by 10%, N max. = 0.9 N v.p.

6) rated power N nom – the highest thermal power of the burner when the performance indicators comply with the established standards, i.e. the highest power with which the burner operates for a long time with high efficiency.

7) range of operating regulation (thermal power of the burner) – a regulated range in which the thermal power of the burner can change during operation, i.e. power values ​​from N min to N nom. .

8) working regulation coefficient K pp. – the ratio of the burner’s rated thermal power to its minimum operating thermal power, i.e. shows how many times the rated power exceeds the minimum: K pp. = N nom./ N min

Regime map.According to the “Rules for the use of gas...”, approved by the RF Government of May 17, 2002 No. 317(amended 06/19/2017) , upon completion of construction and installation work on constructed, reconstructed or modernized gas-using equipment and equipment converted to gas from other types of fuel, commissioning and operational adjustment work is carried out. Supply of gas to constructed, reconstructed or modernized gas-using equipment and equipment converted to gas from other types of fuel to carry out commissioning works (comprehensive testing) and acceptance of equipment into operation is carried out on the basis of a certificate of readiness of gas consumption networks and gas-using equipment of a capital construction facility for connection (technological connection). The rules state that:

· gas-using equipment - boilers, industrial furnaces, technological lines, waste heaters and other installations using gas as fuel in order to generate thermal energy for central heating, hot water supply, in technological processes various industries, as well as other devices, apparatus, units, technological equipment and installations using gas as a raw material;

· commissioning works - complex of works, including preparation for start-up and start-up of gas-using equipment with communications and fittings, bringing the load of gas-using equipment to the level agreed with the organization that owns the equipment, A also adjusting the combustion mode of gas-using equipment without efficiency optimization;

· commissioning work- a set of works, including setting up gas-using equipment in order to achieve the design (certified) efficiency in the range of workloads, adjusting the means automatic regulation fuel combustion processes, heat recovery plants and auxiliary equipment, including water treatment equipment for boiler houses.

According to GOST R 54961-2012 (Gas distribution systems. Gas consumption networks) it is recommended:Operating modes gas-using equipment in enterprises and boiler houses must comply with regime cards , approved by the technical manager of the enterprise and P are produced at least once every three years with adjustments (if necessary) of regime cards .

Unscheduled routine adjustment of gas-using equipment should be carried out in the following cases: after overhaul gas-using equipment or making design changes that affect the efficiency of gas use, as well as in case of systematic deviations of the controlled operating parameters of gas-using equipment from the operating charts.

Classification of gas burners According to GOST gas-burners classified according to: method of supplying the component; degree of preparation of the combustible mixture; flow rate of combustion products; the nature of the mixture flow; nominal gas pressure; degree of automation; possibility of regulating the excess air coefficient and flame characteristics; localization of the combustion zone; the possibility of using the heat of combustion products.

IN chamber furnace of a gas-fired installation gaseous fuel is burned in a flare.

According to the method of air supply, burners can be:

1) Atmospheric burners –air enters the combustion zone directly from the atmosphere:

A. Diffusion – This is the simplest burner in design, which is usually a pipe with holes drilled in one or two rows. Gas enters the combustion zone from the pipe through holes, and air - due to diffusion and gas jet energy (rice. 10 ), all air is secondary .

Advantages of the burner : simplicity of design, reliability of operation ( flame breakthrough is impossible ), quiet operation, good regulation.

Flaws: low power, uneconomical, high (long) flame, combustion stabilizers are required to prevent the burner flame from going out upon separation .

b. Injection - air is injected, i.e. is sucked into the inside of the burner due to the energy of the gas stream emerging from the nozzle . The gas stream creates a vacuum in the nozzle area, where air is sucked in through the gap between the air washer and the burner body. Inside the burner, gas and air are mixed, and the gas-air mixture enters the combustion zone, and the rest of the air necessary for gas combustion (secondary) enters the combustion zone due to diffusion (Fig. 11, 12, 13 ).

Depending on the amount of injected air there are different injection burners: with incomplete and complete pre-mixing of gas and air.

To the burners middle and high pressure gas all the necessary air is sucked in, i.e. all air is primary, complete preliminary mixing of gas with air occurs. A fully prepared gas-air mixture enters the combustion zone and there is no need for secondary air.

To the burners low pressure part of the air necessary for combustion is sucked in (incomplete air injection occurs, this air is primary), and the rest of the air (secondary) enters directly into the combustion zone.

The gas-air ratio in these burners is regulated by the position of the air washer relative to the burner body. Burners are single-flare and multi-flare with central and peripheral gas supply (BIG and BIGm) consisting of a set of tubes - mixers 1 with a diameter of 48x3, united by a common gas manifold 2 (Fig. 13 ).

Advantages of burners: simplicity of design and power control.

Disadvantages of burners: high noise level, possibility of flame slip, small operating control range.

2) Burners with forced air supply - These are burners in which combustion air is supplied from a fan. Gas from the gas pipeline enters the internal chamber of the burner (Fig. 14 ).

Air forced by the fan is supplied to the air chamber 2 , passes through the air swirler 4 , twisted and mixed in the mixer 5 with gas that enters the combustion zone from the gas channel 1 through gas outlets 3 .Combustion takes place in a ceramic tunnel 7 .

Rice. 14. Burner with forced air supply: 1 – gas channel; 2 – air channel; 3 – gas outlets; 4 – swirler; 5 – mixer; 6 – ceramic tunnel (combustion stabilizer).

Rice. 15. Combined single-flow burner: 1 – gas inlet; 2 – fuel oil inlet; 3 – steam inlet and gas outlets; 4 – primary air inlet; 5 – secondary air inlet mixer; 6 – oil-steam nozzle; 7 – mounting plate; 8 - primary air swirler; 9 - secondary air swirler; 10 - ceramic tunnel (combustion stabilizer); 11 – gas channel; 12 - secondary air channel.

Advantages of burners: large thermal power, wide range of operating regulation, the ability to regulate the excess air coefficient, the ability to preheat gas and air.

Disadvantages of burners: sufficient design complexity; flame separation and breakthrough is possible, which makes it necessary to use combustion stabilizers (ceramic tunnel).

Burners designed to burn several types of fuel (gaseous, liquid, solid) are called combined (rice. 15 ). They can be single-threaded or double-threaded, i.e. with one or more gas supplies to the burner.

3) Block burner – this is an automatic burner with forced air (rice. 16 ), assembled with a fan into a single unit. The burner is equipped with an automatic control system.

The fuel combustion process in block burners is controlled electronic device, which is called the combustion manager.

At the burners liquid fuel this block includes fuel pump or fuel pump and fuel heater.

The control unit (combustion manager) controls and monitors the operation of the burner, receiving commands from the thermostat (temperature regulator), flame control electrode and gas and air pressure sensors.

Gas flow is regulated by a butterfly valve located outside the burner body.

The retaining washer is responsible for mixing gas with air in the conical part of the flame tube and is used to regulate the air supply (pressure side adjustment). Another possibility for changing the amount of air supplied is to change the position of the air butterfly valve in the air regulator housing (suction side adjustment).

Regulation of gas-air ratios (control of gas and air butterfly valves) can be:

· connected, from one actuator:

· frequency control of air flow, by changing the rotation speed of the fan motor using an inverter, which consists of frequency converter and a pulse sensor.

The burner is ignited automatically by the ignition device using an ignition electrode. The presence of a flame is monitored by a flame monitoring electrode.

Operating sequence for turning on the burner:

· request for heat generation (from the thermostat);

· turning on the electric motor of the fan and preliminary ventilation of the firebox;

· turning on the electronic ignition;

· opening the solenoid valve, supplying gas and igniting the burner;

· signal from the flame control sensor about the presence of a flame.

Accidents (incidents) on burners. Flame break - movement of the root zone of the torch from the burner outlets in the direction of flow of fuel or combustible mixture. Occurs when the speed of the gas-air mixture or gas becomes greater than the speed of flame propagation. The flame moves away from the burner, becomes unstable and may go out. Gas continues to flow through the extinguished burner and an explosive mixture can form in the firebox.

Separation occurs when: gas pressure increases above the permissible level, a sharp increase in the supply of primary air, or an increase in vacuum in the furnace. For anti-tear protection apply combustion stabilizers (rice. 17): brick slides and pillars; ceramic tunnels various types and brick cracks; poorly streamlined bodies, which become heated during burner operation (when the flame goes out, a fresh stream will ignite from the stabilizer), as well as special pilot burners.

Flame breakthrough - movement of the torch zone towards the combustible mixture, at which the flame penetrates into the burner . This phenomenon occurs only in burners with pre-mixed gas and air and occurs when the speed of the gas-air mixture becomes less than the speed of flame propagation. The flame jumps into the inside of the burner, where it continues to burn, causing deformation of the burner due to overheating.

Surge occurs when: the gas pressure in front of the burner decreases below the permissible level; igniting the burner when supplying primary air; large gas supply at low air pressure. If there is a breakthrough, a slight pop may occur, as a result of which the flame will go out, while gas may continue to flow through the idle burner and an explosive mixture may form in the firebox and flues of the gas-using installation. To protect against slippage, plate or mesh stabilizers are used, because there is no flame penetration through narrow slots and small holes.

Actions of personnel in case of burner accidents

In the event of an accident on the burner (separation, breakthrough or extinguishing of the flame) during ignition or during the regulation process, it is necessary: ​​immediately stop the gas supply to this burner (burners) and the ignition device; ventilate the firebox and flues for at least 10 minutes; find out the cause of the problem; report to the responsible person; After eliminating the causes of the problems and checking the tightness of the shut-off valve in front of the burner, re-ignite according to the instructions of the responsible person.

Changing the burner load.

There are burners with different ways to change the heat output:

Burner with multi-stage heat output control– this is a burner during operation of which the fuel flow regulator can be installed in several positions between the maximum and minimum operating positions.

Burner with three-stage heat output control- this is a burner, during operation of which the fuel flow regulator can be installed in the “maximum flow” - “ minimum consumption" - "closed".

Burner with two-stage heat output control- burner operating in the “open - closed” positions.

Burner with smooth control- this is a burner during operation of which the fuel flow regulator can be installed in any position between the maximum and minimum operating positions.

The thermal power of the installation can be adjusted by the number of operating burners, if provided by the manufacturer and the regime card.

Changing heat output manually, in order to avoid flame separation, the following is performed:

When increasing: first increase the gas supply, and then the air.

When decreasing: first reduce the air supply, and then the gas;

To prevent accidents on burners, changing their power must be done smoothly (in several steps) according to the regime map.