Conditions for ignition and combustion of gas fuel. Products of combustion of domestic gas and household activities Products of combustion of natural gas
The main condition for gas combustion is the presence of oxygen (and therefore air). Without the presence of air, gas combustion is impossible. During gas combustion, chemical reaction compounds of oxygen in the air with carbon and hydrogen in the fuel. The reaction occurs with the release of heat, light, and carbon dioxide and water vapor.
Depending on the amount of air involved in the gas combustion process, complete or incomplete combustion occurs.
With sufficient air supply, complete combustion of the gas occurs, as a result of which its combustion products contain non-combustible gases: carbon dioxide C02, nitrogen N2, water vapor H20. Most of all (by volume) in the combustion products of nitrogen is 69.3-74%.
For complete combustion gas, it is also necessary that it be mixed with air in certain (for each gas) quantities. The higher the calorific value of the gas, the greater the amount of air required. Thus, to burn 1 m3 of natural gas, about 10 m3 of air is required, artificial - about 5 m3, mixed - about 8.5 m3.
If there is insufficient air supply, incomplete combustion of gas occurs or chemical underburning flammable components; Combustible gases appear in combustion products: carbon monoxide CO, methane CH4 and hydrogen H2
With incomplete combustion of gas, a long, smoky, luminous, opaque, yellow color torch.
Thus, a lack of air leads to incomplete combustion of the gas, and an excess leads to excessive cooling of the flame temperature. The ignition temperature of natural gas is 530 °C, coke gas - 640 °C, mixed gas - 600 °C. In addition, with a significant excess of air, incomplete combustion of gas also occurs. In this case, the end of the torch is yellowish in color, not completely transparent, with a vague bluish-green core; the flame is unstable and comes off the burner.
Rice. 1. Gas flame - without preliminary mixing of gas with air; b -c partial prev. verifiable mixing of gas with air; c - with preliminary complete mixing of gas with air; 1 - inner dark zone; 2 - smoky luminous cone; 3 - burning layer; 4 - combustion products
In the first case (Fig. 1a), the torch is longer and consists of three zones. Pure gas burns in atmospheric air. In the first inner dark zone, the gas does not burn: it is not mixed with oxygen in the air and is not heated to the ignition temperature. Air enters the second zone in insufficient quantities: it is retained by the burning layer, and therefore it cannot mix well with the gas. This is evidenced by the brightly glowing, light yellow, smoky color of the flame. Air enters the third zone in sufficient quantities, the oxygen of which mixes well with the gas, the gas burns bluish.
With this method, gas and air are supplied to the furnace separately. In the firebox, not only the combustion of the gas-air mixture occurs, but also the process of preparing the mixture. This method of gas combustion is widely used in industrial installations.
In the second case (Fig. 1.6), gas combustion occurs much better. As a result of partial preliminary mixing of gas with air, the prepared gas-air mixture enters the combustion zone. The flame becomes shorter, non-luminous, and has two zones - internal and external.
The gas-air mixture in the inner zone does not burn, since it was not heated to the ignition temperature. In the outer zone, the gas-air mixture burns, while in the upper part of the zone the temperature rises sharply.
With partial mixing of gas with air, in this case, complete combustion of the gas occurs only with additional air supply to the torch. During gas combustion, air is supplied twice: the first time before entering the furnace (primary air), the second time directly into the furnace (secondary air). This method of gas combustion is the basis for the design of gas burners for household appliances and heating boiler houses.
In the third case, the torch is significantly shortened and the gas burns more completely, since the gas-air mixture has been previously prepared. A short transparent flame indicates the completeness of gas combustion blue color(flameless combustion), which is used in infrared radiation devices for gas heating.
- Gas combustion process
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 - freezes at low temperatures, forming ice plugs, which leads to freezing of 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: density atmospheric air under normal conditions - 1.29 kg/m 3, 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 for 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: the lowest - QH = 8500 kcal/m 3, the highest - Qb - 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 of coal was taken to be equal to 29.3 MJ or 7000 kcal/kg.
Conditions for measuring gas flow are::
· normal conditions(n. at): standard physical conditions to which the properties of substances are usually related. Normal conditions are defined by IUPAC (International Union of Practical and Applied Chemistry) in the following way: 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 working area 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 in 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 hydrocarbon gases – chemical combination of flammable gas components (carbon C and hydrogen H) with atmospheric 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 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 a larger quantity 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 units of 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. The vacuum in the furnace and the removal of combustion products are produced by a draft force that overcomes the resistance of the smoke path and arises 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 chimney, and in their place cold air enters the firebox (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 with insufficient natural draft. 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 the supply of the required amount of gas and air, mix them and regulate the combustion process, and equipped with a tunnel, air distribution device, etc., are called gas burner devices.
Burner requirements:
1) burners must meet the requirements of the relevant technical regulations(have a certificate or declaration of conformity) or undergo an examination industrial safety;
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. maximum power with which the burner operates 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 object capital construction to the 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 of various industries, as well as other devices, apparatus, units, technological equipment and installations using gas as a feedstock;
· 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 are 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 by an electronic device called a combustion manager.
For liquid fuel burners, this unit includes a fuel pump or a fuel pump and a 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 regulation air flow by changing the rotation speed of the fan electric 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 of various types and brick slots; 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 changes in thermal power:
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.
Physico-chemical properties of natural gas
Natural gas is colorless, odorless, tasteless and 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 in the open air.
When gas is burned with underburning, i.e., with a lack of oxygen, carbon monoxide (CO), or carbon monoxide, which is a highly toxic gas, is formed in the combustion products.
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 is a chemical process of combining 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).
Stages of combustion: supply of gas and air, formation of a 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 the premises, can cause poisoning of operating 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 of gas, combustion air is supplied in sufficient quantity, 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.
Burner equipped 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. It consists of a gas manifold made of a 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.
Disadvantages: low power, uneconomical, high flame.
a) low pressure or atmospheric (applies to burners with partial pre-mixing). 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 breaks down. 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 suppresses noise caused by high speed 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 noise level.
3) Burners with forced air supply. 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 the outer surface of the 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,
- find out the cause of the accident,
- make a journal entry,
Section Contents
When organic fuels are burned in boiler furnaces, various combustion products are formed, such as carbon oxides CO x = CO + CO 2, water vapor H 2 O, sulfur oxides SO x = SO 2 + SO 3, nitrogen oxides NO x = NO + NO 2 , polycyclic aromatic hydrocarbons (PAHs), fluoride compounds, vanadium compounds V 2 O 5, solid particles, etc. (see Table 7.1.1). When fuel is incompletely burned in furnaces, the exhaust gases may also contain hydrocarbons CH4, C2H4, etc. All products of incomplete combustion are harmful, but with modern fuel combustion technology their formation can be minimized [1].
Table 7.1.1. Specific emissions from flaring combustion of organic fuels in power boilers [3]
Legend: A p, S p – respectively, the content of ash and sulfur per working mass of fuel, %.
The criterion for sanitary assessment of the environment is the maximum permissible concentration (MPC) of a harmful substance in the atmospheric air at ground level. MPC should be understood as such a concentration various substances and chemical compounds, which, when exposed to the human body daily for a long time, does not cause any pathological changes or diseases.
Maximum permissible concentrations (MPC) of harmful substances in the atmospheric air of populated areas are given in table. 7.1.2 [4]. The maximum single concentration of harmful substances is determined by samples taken within 20 minutes, the average daily concentration - per day.
Table 7.1.2. Maximum permissible concentrations of harmful substances in the atmospheric air of populated areas
| Pollutant | Maximum permissible concentration, mg/m3 | |
| Maximum one-time | Average daily | |
| Dust is non-toxic | 0,5 | 0,15 |
| Sulfur dioxide | 0,5 | 0,05 |
| Carbon monoxide | 3,0 | 1,0 |
| Carbon monoxide | 3,0 | 1,0 |
| Nitrogen dioxide | 0,085 | 0,04 |
| Nitric oxide | 0,6 | 0,06 |
| Soot (soot) | 0,15 | 0,05 |
| Hydrogen sulfide | 0,008 | 0,008 |
| Benz(a)pyrene | - | 0.1 µg/100 m 3 |
| Vanadium pentoxide | - | 0,002 |
| Fluoride compounds (by fluorine) | 0,02 | 0,005 |
| Chlorine | 0,1 | 0,03 |
Calculations are carried out for each harmful substance separately, so that the concentration of each of them does not exceed the values given in table. 7.1.2. For boiler houses, these conditions have been tightened by introducing additional requirements about the need to sum up the effects of sulfur and nitrogen oxides, which is determined by the expression
At the same time, due to local air deficiencies or unfavorable thermal and aerodynamic conditions, incomplete combustion products are formed in the furnaces and combustion chambers, consisting mainly of carbon monoxide CO (carbon monoxide), hydrogen H 2 and various hydrocarbons, which characterize heat loss in boiler unit from chemical incomplete combustion (chemical underburning).
In addition, the combustion process produces a number of chemical compounds formed due to the oxidation of various components of the fuel and air nitrogen N2. The most significant part of them consists of nitrogen oxides NO x and sulfur oxides SO x .
Nitrogen oxides are formed due to the oxidation of both molecular nitrogen in the air and nitrogen contained in the fuel. Experimental studies have shown that the main share of NO x formed in boiler furnaces, namely 96÷100%, is nitrogen monoxide (oxide) NO. NO 2 dioxide and nitrogen hemioxide N 2 O are formed in significantly smaller quantities, and their share is approximately: for NO 2 - up to 4%, and for N 2 O - hundredths of a percent of the total NO x emission. Under typical conditions of flaring fuel in boilers, the concentrations of nitrogen dioxide NO 2 are usually negligible compared to the NO content and usually range from 0÷7 ppm up to 20÷30 ppm. At the same time, rapid mixing of hot and cold regions in a turbulent flame can lead to the appearance of relatively large concentrations of nitrogen dioxide in the cold zones of the flow. In addition, partial emission of NO 2 occurs in the upper part of the furnace and in the horizontal flue (with T> 900÷1000 K) and under certain conditions can also reach noticeable sizes.
Nitrogen hemioxide N 2 O, formed during the combustion of fuels, is, apparently, a short-term intermediate substance. N 2 O is practically absent in combustion products behind boilers.
The sulfur contained in the fuel is a source of the formation of sulfur oxides SO x: sulfur dioxide SO 2 (sulfur dioxide) and sulfur SO 3 (sulfur trioxide) anhydrides. The total mass emission of SO x depends only on the sulfur content in the fuel S p , and their concentration in the flue gases also depends on the air flow coefficient α. As a rule, the share of SO 2 is 97÷99%, and the share of SO 3 is 1÷3% of the total yield of SO x. The actual SO 2 content in the gases leaving the boilers ranges from 0.08 to 0.6%, and the SO 3 concentration ranges from 0.0001 to 0.008%.
Among harmful components flue gases occupy a special place large group polycyclic aromatic hydrocarbons (PAHs). Many PAHs have high carcinogenic and (or) mutagenic activity and activate photochemical smog in cities, which requires strict control and limitation of their emissions. At the same time, some PAHs, for example, phenanthrene, fluoranthene, pyrene and a number of others, are physiologically almost inert and are not carcinogenic.
PAHs are formed as a result of incomplete combustion of any hydrocarbon fuels. The latter occurs due to the inhibition of oxidation reactions of fuel hydrocarbons by the cold walls of combustion devices, and can also be caused by unsatisfactory mixing of fuel and air. This leads to the formation of local oxidation zones in the furnaces (combustion chambers) with low temperature or areas with excess fuel.
Due to large quantity of different PAHs in flue gases and the difficulty of measuring their concentrations, it is customary to estimate the level of carcinogenic contamination of combustion products and atmospheric air by the concentration of the most powerful and stable carcinogen - benzo(a)pyrene (B(a)P) C 20 H 12 .
Due to their high toxicity, special mention should be made of fuel oil combustion products such as vanadium oxides. Vanadium is contained in the mineral part of fuel oil and, when burned, forms vanadium oxides VO, VO 2. However, when deposits form on convective surfaces, vanadium oxides are presented mainly in the form of V 2 O 5. Vanadium pentoxide V 2 O 5 is the most toxic form of vanadium oxides, therefore their emissions are calculated in terms of V 2 O 5.
Table 7.1.3. Approximate concentration of harmful substances in combustion products during flaring of organic fuels in power boilers
| Emissions = | Concentration, mg/m 3 | ||
| Natural gas | Fuel oil | Coal | |
| Nitrogen oxides NO x (in terms of NO 2) | 200÷ 1200 | 300÷ 1000 | 350 ÷1500 |
| Sulfur dioxide SO2 | - | 2000÷6000 | 1000÷5000 |
| Sulfuric anhydride SO 3 | - | 4÷250 | 2 ÷100 |
| Carbon monoxide CO | 10÷125 | 10÷150 | 15÷150 |
| Benz(a)pyrene C 20 H 12 | (0.1÷1, 0)·10 -3 | (0.2÷4.0) 10 -3 | (0.3÷14) 10 -3 |
| Particulate matter | - | <100 | 150÷300 |
When burning fuel oil and solid fuel, emissions also contain solid particles consisting of fly ash, soot particles, PAHs and unburned fuel as a result of mechanical underburning.
The ranges of concentrations of harmful substances in flue gases when burning various types of fuels are given in table. 7.1.3.
Alexander Pavlovich Konstantinov
Chief Inspector for Safety Control of Nuclear and Radiation Hazardous Facilities. Candidate of Technical Sciences, Associate Professor, Professor of the Russian Academy of Natural Sciences.
A kitchen with a gas stove is often the main source of air pollution throughout the apartment. And, what is very important, this applies to the majority of Russian residents. Indeed, in Russia, 90% of urban and over 80% of rural residents use gas stoves Khata, Z. I. Human health in the modern environmental situation. - M.: FAIR PRESS, 2001. - 208 p..
In recent years, publications by serious researchers have appeared on the high health hazards of gas stoves. Doctors know that in houses with gas stoves, residents get sick more often and for longer than in houses with electric stoves. Moreover, we are talking about many different diseases, and not just respiratory diseases. The decline in health is especially noticeable in women, children, as well as in older and chronically ill people who spend more time at home.
It was not for nothing that Professor V. Blagov called the use of gas stoves “a large-scale chemical war against one’s own people.”
Why using domestic gas is harmful to health
Let's try to answer this question. There are several factors that combine to make the use of gas stoves hazardous to health.
First group of factors
This group of factors is determined by the very chemistry of the natural gas combustion process. Even if household gas burned completely to water and carbon dioxide, this would lead to a deterioration in the composition of the air in the apartment, especially in the kitchen. After all, at the same time, oxygen is burned out of the air, and at the same time the concentration of carbon dioxide increases. But this is not the main problem. In the end, the same thing happens to the air that a person breathes.
It is much worse that in most cases gas combustion does not occur completely, not 100%. Due to incomplete combustion of natural gas, much more toxic products are formed. For example, carbon monoxide (carbon monoxide), the concentration of which can be many times, 20–25 times higher than the permissible limit. But this leads to headaches, allergies, ailments, weakened immunity Yakovleva, M. A. And we have gas in our apartment. - Business environmental magazine. - 2004. - No. 1(4). - P. 55..
In addition to carbon monoxide, sulfur dioxide, nitrogen oxides, formaldehyde, and benzopyrene, a strong carcinogen, are released into the air. In cities, benzopyrene enters the air from emissions from metallurgical plants, thermal power plants (especially coal-fired ones) and cars (especially old ones). But the concentration of benzopyrene, even in polluted atmospheric air, cannot be compared with its concentration in an apartment. The figure shows how much more benzopyrene we get while in the kitchen.
Entry of benzopyrene into the human body, mcg/day Let's compare the first two columns. In the kitchen we get 13.5 times more harmful substances than on the street! For clarity, let us estimate the intake of benzopyrene into our body not in micrograms, but in a more understandable equivalent - the number of cigarettes smoked daily. So, if a smoker smokes one pack (20 cigarettes) per day, then in the kitchen a person receives the equivalent of two to five cigarettes per day. That is, a housewife who has a gas stove seems to “smoke” a little.
Second group of factors
This group is related to the operating conditions of gas stoves. Any driver knows that you cannot be in the garage at the same time as a car with the engine running. But in the kitchen we have just such a case: burning hydrocarbon fuels indoors! We lack that device that every car has - an exhaust pipe. According to all hygiene rules, each gas stove must be equipped with an exhaust ventilation hood.
Things are especially bad if we have a small kitchen in a small apartment. Minimum area, minimal ceiling height, poor ventilation and a gas stove running all day. But with low ceilings, gas combustion products accumulate in the upper layer of air up to 70–80 centimeters thick Boyko, A. F. Health 5+. - M.: Rossiyskaya Gazeta, 2002. - 365 p..
The work of a housewife at a gas stove is often compared to harmful working conditions in production. This is not entirely correct. Calculations show that if the kitchen is small and there is no good ventilation, then we are dealing with particularly harmful working conditions. A type of metallurgist servicing coke oven batteries.
How to reduce harm from a gas stove
What should we do if everything is so bad? Maybe it’s really worth getting rid of the gas stove and installing an electric or induction one? It's good if there is such an opportunity. And if not? There are several simple rules for this case. It is enough to follow them, and you can reduce the harm to health from a gas stove tenfold. Let us list these rules (most of them are the recommendations of Professor Yu. D. Gubernsky) Ilnitsky, A. It smells like gas. - Be healthy!. - 2001. - No. 5. - P. 68–70..
- It is necessary to install an exhaust hood with an air purifier above the stove. This is the most effective technique. But even if for some reason you cannot do this, then the remaining seven rules in total will also significantly reduce air pollution.
- Monitor the complete combustion of gas. If suddenly the color of the gas is not what it should be according to the instructions, immediately call gas workers to regulate the malfunctioning burner.
- Do not clutter the stove with unnecessary dishes. Cookware should only be placed on working burners. In this case, free access of air to the burners and more complete combustion of gas will be ensured.
- It is better to use no more than two burners or an oven and one burner at the same time. Even if your stove has four burners, it is better to turn on a maximum of two at a time.
- The maximum continuous operation time of a gas stove is two hours. After this, you need to take a break and thoroughly ventilate the kitchen.
- When the gas stove is operating, the doors to the kitchen should be closed and the window should be open. This will ensure that combustion products are removed through the street, and not through living rooms.
- After finishing operation of the gas stove, it is advisable to ventilate not only the kitchen, but the entire apartment. Through ventilation is desirable.
- Never use a gas stove to heat or dry clothes. You wouldn’t start a fire in the middle of the kitchen for this purpose, right?