What are the concentration limits of the explosiveness of ammonia in air. Physical and chemical properties of natural gas. FM marking according to NEC, CEC
1. The gas is colorless, tasteless and odorless. Non-poisonous, non-toxic. It has a suffocating effect, i.e. in case of leaks, it displaces oxygen from the volume of the premises.
2. Fire and explosion hazardous.
3. Approximately two times lighter than air, therefore, in case of leaks, it accumulates in the upper layers of the premises.
Air Density:rair.=1.29 kg/m 3 .
Gas Density:rgas.=0.72 kg/m 3 .
4. At a temperature of -162 ° C and atmospheric pressure (760 mmhg. Art.) natural gas turns into a liquid state.
5. The temperature developed during the combustion of gas is from +1600 to +2000 ° C.
6. Ignition temperature +645 ° C.
7. The combustion of one cubic meter of gas releases 8500 kcal of heat (calorific value of natural gas).
8. Gas explosion limits: 5% to 15% by volume.
If the concentration of gas in indoor air is less than 5% or more than 15%, there will be no explosion. There will be fire or fire. When less than 5% - there will be a lack of gas and less heat that supports combustion.
In the second case (concentration over 15%) there will be little air, i.e. oxidizer, and a small amount of heat to sustain combustion.
General characteristics of the fuel. Compound. Heat of combustion of fuel.
Fuel- these are combustible substances, the main component of which is carbon, used to obtain thermal energy by burning them.
As fuel use:
Natural gas extracted from gas fields;
Associated gas obtained during the development of oil fields;
Liquefied hydrocarbon gases obtained from the processing of associated oil fields and gases produced from gas condensate fields
The largest gas fields in Russia: Urengoy, Stavropol, Syzran, etc.
Natural gases are homogeneous in composition and consist mainly of methane. Associated gases from oil fields also contain ethane, propane and butane. Liquefied gases are a mixture of propane and butane, and gases obtained at oil refineries during the thermal processing of oil, in addition to propane and butane, contain ethylene, propylene and butylene.
In addition to combustible components, natural gases contain large amounts of hydrogen sulfide, oxygen, nitrogen, carbon dioxide, water vapor and mechanical impurities.
The normal operation of gas appliances depends on the constancy of the composition of the gas and the number of harmful impurities contained in it.
According to GOST 5542-87, combustible substances of natural gases are characterized by the Wobbe number, which is the ratio of the heat of combustion to the square root of the relative (in air) gas density:
Basic properties of gases.
The specific gravity of air is 1.293 kg/m3.
Natural gas methane CH4, specific gravity 0.7 kg / m3, lighter than air by 1.85 times, so it accumulates in the upper part of the room or well.
Liquefied gas propane-butane mixture (propane С3Н8, butane С4Н10) has a specific gravity in the liquid state of 0.5 t / m3, in the gaseous state of 2.2 kg / m3.
Heating capacity.
With the complete combustion of one cubic meter of gas, 8-8.5 thousand kilocalories are released;
Liquefied gas propane-butane 24-28 thousand kilocalories
The combustion temperature of gases is +2100 degrees C.
Natural and liquefied gases mixed with air are explosive.
Explosive limits of gas-air mixtures.
Up to 5% ignition does not occur
5% to 15% explosion occurs
Over 15% if there is a source of fire, it will ignite and burn
Sources of ignition of the gas-air mixture
● open fire (matches, cigarettes);
● Electric spark that occurs when turning on and off any electrical appliance;
● A spark generated by the friction of a tool against a piece of gas equipment or when metal objects hit each other
Natural and liquefied gases are colorless and odorless. Ethyl mercaptan, a substance that has the characteristic odor of sauerkraut, is added to make it easier to detect a gas leak.
Explosive limits of gas-air mixtures
Excluding the formation of explosive gas-air concentrations, as well as the appearance of sources of ignition of this mixture (flames, sparks) is always the main task of the maintenance personnel of compressor stations. When the gas-air mixture explodes, the pressure in the explosion zone rises sharply, leading to the destruction of building structures, and the flame propagation speed reaches hundreds of meters per second. For example, the auto-ignition temperature of a methane-air mixture is at the level of 700 °C, and methane is the main component of natural gas. Its content in gas fields fluctuates in the range of 92-98%.
During the explosion of a gas-air mixture under a pressure of 0.1 MPa, a pressure of about 0.80 MPa develops. The gas-air mixture explodes if it contains 5-15% methane; 2-10% propane; 2-9% butane, etc. With an increase in the pressure of the gas-air mixture, the explosive limits narrow. It should be noted that the admixture of oxygen in the gas increases the risk of explosion.
The limits and range of explosiveness of gases in a mixture with air at a temperature of 20 ° C and a pressure of 0.1 MPa are given in Table. 1.4.
Table 1.4
Limits and range of explosion of gases in a mixture with air at a temperature of 20 ° C and a pressure of 0.1 MPa
|
Explosive limits, % by volume |
Explosive interval, % by volume |
||
|
Acetylene | |||
|
Oilfield. gas | |||
|
carbon monoxide | |||
|
Natural gas | |||
|
Propylene | |||
1.2. Laws of ideal gases. Areas of their application
Ideal gases are considered to be gases that obey the Clapeyron equation (). At the same time, ideal gases mean gases in which there are no forces of intermolecular interaction, and the volume of the molecules themselves is zero. At present, it can be argued that none of the real gases obeys these gas laws. Nevertheless, these specific gas laws are widely used in technical calculations. These laws are simple and quite well characterize the behavior of real gases at low pressures and not very low temperatures, far from saturation regions and critical points of matter. The laws of Boyle-Mariotte, Gay-Lussac, Avogadro and, based on them, the Clapeyron-Mendeleev equation received the greatest practical distribution.
Boyle-Mariotge's law states that at constant temperature ( 
= const) the product of absolute pressure and specific volume of an ideal gas remains constant ( 
= const), i.e. The product of absolute pressure and specific volume depends only on temperature. Where at 
= const we have:
.
(1.27)
Gay-Lussac's law states that at constant pressure ( 
= const) the volume of an ideal gas changes in direct proportion to the temperature increase:
,
(1.28)
where 
- specific volume of gas at temperature 
°С and pressure 
- specific volume of gas at temperature 
= 0 °С and the same pressure 
;
- temperature coefficient of volumetric expansion of ideal gases at 0 ° C, which remains the same value at all pressures and is the same for all ideal gases:
.
(1.29)
Thus, the content of the Gay-Lussac law is reduced to the following statement: the volumetric expansion of ideal gases with a change in temperature and with 
= const is linear, and the temperature coefficient of volume expansion 
is the universal constant of ideal gases.
Comparison of the laws of Boyle-Mariotte and Gay-Lussac leads to the equation of state for ideal gases:
,
(1.30)
where 
- specific volume of gas; 
- absolute gas pressure; 
- specific gas constant of an ideal gas; 
is the absolute temperature of an ideal gas:
.
(1.31)
The physical meaning of the specific gas constant 
is specific work in progress 
= const when the temperature changes by one degree.
Avogadro's law states that the volume of one mole of an ideal gas 
does not depend on the nature of the gas and is completely determined by the pressure and temperature of the substance ( 
). On this basis, it is argued that the volumes of moles of different gases, taken at the same pressures and temperatures, are equal to each other. If a 
is the specific volume of gas, and 
- molar mass, then the volume of a mole (molar volume) is equal to 
. At equal pressures and temperatures for different gases, we have:
Since the specific molar volume of gas 
depends in the general case only on pressure and temperature, then the product 
in equation (1.32) - there is a value that is the same for all gases and therefore is called the universal gas constant:
, J/kmol K. (1.33)
From equation (1.33) it follows that the specific gas constants of individual gases 
are determined in terms of their molar masses. For example, for nitrogen ( 
) the specific gas constant will be
= 8314/28 = 297 J/(kg K). (1.34)
For 
kg of gas, taking into account the fact that 
, the Clapeyron equation is written as:
,
(1.35)
where 
- amount of substance in moles 
. For 1 kmole of gas:
.
(1.36)
The last equation obtained by the Russian scientist D.I. Mendeleev is often called the Clapeyron-Mendeleev equation.
The value of the molar volume of ideal gases under normal physical conditions ( 
= 0 °С and 
= 101.1 kPa) will be:
= 22.4 m 
/kmol. (1.37)
The equation of state of real gases is often written on the basis of the Clapeyron equation with the introduction of a correction into it 
, which takes into account the deviation of the real gas from the ideal
,
(1.38)
where 
- compressibility factor, determined by special nomograms or from the relevant tables. On fig. 1.1 shows a nomogram for determining the numerical values of the quantity 
natural gas depending on pressure 
, relative density of gas in air 
and its temperature 
. In the scientific literature, the compressibility factor 
usually determined depending on the so-called reduced parameters (pressure and temperature) of the gas:
;
,
(1.39)
where 
,
and 
- respectively reduced, absolute and critical gas pressure; 
,
and 
are the reduced, absolute and critical gas temperatures, respectively.
Rice. 1.1. Calculation nomogram 
depending on the 
,
,
The critical pressure is the pressure at which and above which no increase in temperature can cause the liquid to be converted into vapor.
The critical temperature is the temperature at which and above which no vapor can be condensed under any increase in pressure.
Numerical values of critical parameters for some gases are given in Table. 1.5.
Table 1.5
| – | Lower explosive limit | Upper explosion limit |
| Gasoline B-70 | 0,8 | 5,1 |
| Tractor kerosene | 1,4 | 7,5 |
| Propane | 2,1 | 9,5 |
| n-butane | 1,5 | 8,5 |
| Methane | 5 | 15 |
| Ammonia | 15 | 28 |
| hydrogen sulfide | 4,3 | 45,5 |
| Carbon monoxide | 12,5 | 75 |
| Hydrogen | 4 | 75 |
| Acetylene | 2 | 82 |
An explosion is an instantaneous chemical transformation, accompanied by the release of energy and the formation of compressed gases.
During explosions of gas-air mixtures, a large amount of heat is released and a large amount of gases is formed.
Due to the released heat, the gases are heated to a high temperature, sharply increase in volume and, expanding, press with great force on the building envelope or the walls of the apparatus in which the explosion occurs.
The pressure at the moment of explosion of gas mixtures reaches 10 kgf/cm 2 , the temperature fluctuates between 1500-2000°C, and the speed of propagation of the explosive wave reaches several hundred meters per second. Explosions tend to cause great destruction and fires.
The fire hazard properties of combustible substances are characterized by a number of indicators: flash point, ignition, self-ignition, etc.
Other properties of combustible substances include explosion pressure, the minimum explosive oxygen content, below which ignition and combustion of the mixture become impossible at any concentration of combustible substance in the mixture, the nature of interaction with fire extinguishing agents, etc.
"Occupational health and safety in the gas industry",
A.N. Yanovich, A.Ts. Astvatsaturov, A.A. Busurin
Indicators Methane Propane n-Butane Aviation gasoline Tractor kerosene Industrial oil Vapor flash point, °С —188 — —77 —34 27 200 Autoignition temperature, °С 537 600—588 490—569 300 250 380 .3-15 2.2-9.5 1.9-8.5 0.8-5.2 1.4-7.5 1-4 —(77/52) —(34/4) 27—69 146—191 Speed…
Explosive concentrations of liquefied and natural gases are formed during the shutdown of pipelines, tanks and apparatuses, when the gas is not completely removed and when it mixes with the incoming air, an explosive mixture is created. In this regard, before starting work, gas pipelines and tanks are washed with water, steamed, and purged with an inert gas. To prevent gas from other tanks or pipelines from being repaired ...
An analysis of fires that have occurred at operated cluster bases of liquefied gas indicates that the main types of accidents are the following: the presence of gas leaks, ruptures of pipelines and flexible hoses, breakdowns of flange connections and failures of plugs, breakdowns of stuffing box seals on stop valves, loosely closed valves, destruction of liquefied gas tanks due to their overflow; various breakdowns on pipelines and tanks (destruction ...
When the gas evaporates, an explosive gas-air mixture is formed. In case of accidents in premises, explosive concentrations of gas occur first of all, near the place of gas leakage, and then spread throughout the premises. When gas evaporates in open areas near the leak, a gas contamination zone is formed that spreads throughout the warehouse. The size of the gas contamination zone during an emergency outflow of gas depends on many ...
The main difficulty in extinguishing gas fires is the fight against gas contamination and re-ignition after extinguishing a fire. No known extinguishing agent eliminates the risk of gassing and re-ignition. The main task in the fight against gas fires is the localization of the fire. It must be carried out by limiting the time of expiration and the volume of the escaping gas, as well as by thermal protection ...
It is known that there is a certain limit value for the concentration of flammable substances in the surrounding atmosphere, which is called the lower explosive limit (LEL). If the concentration of flammable components in the air is below the LEL, then ignition is not possible: the mixture is not flammable. However, the LEL values that are given in the reference literature are usually determined for a normal temperature of 20 °C. When designing gas control systems for operation in a high temperature environment, can it be assumed that methane, propane and other combustible gases retain the LEL values known to us, at a temperature of, for example, 150 ° C?
No. Indeed, with an increase in temperature, the values of the LEL of combustible gases decrease.
Let's find out what LEL concentration really means: it is the minimum concentration of flammable substances in the air at ambient temperature sufficient to initiate a self-sustained combustion. All the energy necessary to maintain combustion is released during the oxidation reaction (heat of combustion). When the concentration of the substance is below the LEL level, there is not enough energy to maintain combustion. We can state that the heat of combustion is necessary to heat the gas mixture from the ambient air temperature to the flame temperature. However, at high ambient temperatures, it will take less energy to heat the gas mixture to flame temperature, or in other words, you will need fewer flammable substances to get self-sustaining combustion. That is, as the temperature rises, the LEL decreases.
For most hydrocarbons, it has been found that LEL decreases at a rate of 0.14% LEL per degree. This speed value already includes a safety margin (equal to 2) to obtain a temperature dependence that is valid for all combustible gases and vapors.
Thus, at ambient temperature t, the LEL can be calculated using the following approximate formula:
LEL(t) = LEL(20°C)*(1 – 0.0014*(t – 20))
Naturally, this formula can only be applied to temperatures below the ignition temperature of a given gas.
The LEL of methane at normal temperature (20 °C) is 4.4% by volume.
At a temperature of 150 °C, the LEL of methane will be:
LEL(150°C) = 4.4*(1 - 0.0014*(150 - 20)) = 4.4*(1 - 0.0014*130) = 4.4*(1-0.182) = 3.6% v/v .d.
Dependence of the lower explosive limit of combustible gases on temperature
Dependence of the lower explosive limit of combustible gases on temperature It is known that there is a certain limit value for the concentration of flammable substances in the surrounding atmosphere, which
Occupational health and safety
Occupational health and safety
Labor protection in conditions of increased danger
Gas economy. Operation of gas equipment
Operation of gas equipment
In industry, along with the use of artificial gases, natural gas is increasingly being used. In its pure form, it has no color and odor, but after odorization, the gas acquires the smell of rotten eggs, by which its presence in the air is determined.
This gas, like many of its analogues, consists of the following components: methane - 90%, nitrogen - 5%, oxygen - 0.2%, heavy hydrocarbons - 4.5%, carbon dioxide - 0.3%.
If a mixture of air and gas is formed in an amount of at least a certain minimum, then the gas may explode. This minimum is called the lower explosive limit and is equal to 5% of the gas content in the air.
When the gas content of this mixture exceeds the maximum amount, the mixture becomes non-explosive. This maximum is called the upper explosive limit and is equal to 15% of the gas content in the air. Mixtures with a gas content lying within the specified range from 5 to 15%, in the presence of various sources of ignition (open flames, sparks, hot objects, or when this mixture is heated to a self-ignition temperature), lead to an explosion.
The ignition temperature of natural gas is 700 0 C. This temperature is significantly reduced due to the catalytic action of certain materials and heated surfaces (water vapor, hydrogen, sooty carbon deposits, hot fireclay surface, etc.). Therefore, to prevent explosions, it is necessary, firstly, to prevent the formation of a mixture of air with gases, i.e., to ensure reliable sealing of all gas devices and maintain positive pressure in them. Secondly, do not allow the gas to come into contact with any source of ignition.
As a result of incomplete combustion of natural gas, carbon monoxide CO is formed, which has a toxic effect on the human body. The permissible content of carbon monoxide in the atmosphere of industrial premises should not exceed 0.03. mg/l.
Each employee of the gas facilities of the enterprise is obliged to undergo special training and certification, to know the operating instructions for his workplace at the enterprise. For all gas hazardous places and gas hazardous work, a list is compiled, agreed with the head of the gas facilities of the plant, the safety department, which is approved by the chief engineer and posted at workplaces.
In the gas industry, success, trouble-free operation and safety of work are ensured by thorough knowledge of the matter, high work organization and discipline. No work not provided for by the job description, without the instructions or permission of the head and the necessary preparation, can be carried out. Gas workers in all cases should not leave their jobs without the knowledge and permission of their foreman. They are obliged to promptly, immediately report to the master about any comments, even the most minor malfunctions.
In the boiler room and other gas-powered units, the following should be hung out:
- An instruction that defines the duties and actions of personnel both in normal operation and in emergency situations.
- List of operators with numbers and expiration dates of their certificates for the right to work and a schedule for going to work.
- A copy of the order or an extract from it on the appointment of a person responsible for the gas sector, his office and home phone numbers.
At the unit in the office there are logs: watch keeping, preventive repairs and inspections, records of control results.
As practice shows, most accidents and accidents at gas-fired units are associated with violation of the Rules, instructions, and the procedure for preparing to turn on the units and ignite the burners.
Before each start-up of boilers, furnaces and other units, their furnaces must be ventilated. The duration of this operation is determined by local regulations and is taken depending on the volume of the furnace and the length of the chimneys.
The smoke exhauster and the fan for supplying air to the burners are switched on when the furnaces and chimneys are ventilated. Prior to this, by rotating the smoke exhauster rotor manually, make sure that it does not touch the body and cannot cause sparks upon impact. Responsible work before starting gas is also purging gas pipelines. Prior to purging, make sure that there are no people in the zone of gas release from the purge candle, there are no light lamps and no open fire work is being carried out.
The end of the purge is determined by analyzing the gas leaving the purge gas pipeline, in which the oxygen content should not exceed 1%.
Before lighting the burners, check:
- The presence of sufficient gas pressure in the gas pipeline in front of the boiler or other unit.
- Air pressure when it is supplied from blowing devices.
- The presence of vacuum in the furnace or hog (to the gate).
If necessary, adjust the tension.
The device that cuts off the gas supply in front of the burner should be opened smoothly and only after an igniter or torch has been brought to it. At the same time, the person performing this work should be on the side of the gas burner at the time of ignition of the gas. When igniting the gas on the burner, the smallest amount of air should be supplied to the furnace, upon receipt of which complete combustion of the gas would be ensured. Other burners are ignited in the same way. If, during ignition, regulation or operation, the flame goes out or it breaks off, flashes, it is necessary to immediately turn off the gas, ventilate the furnace and re-ignite in the order indicated above.
Violation of this requirement is one of the main causes of accidents.
It is forbidden to operate gas-fired units in case of any malfunctions, lack of traction, and also to leave the units switched on for work unattended.
Emergency shutdown of units operating on gas fuel is carried out immediately in cases of gas supply interruption; when the blower fans stop; in case of dangerous gas leakage into the room; in the event of a fire threat or outbreak.
During the preparation of repairs, the manager responsible for their implementation draws up a plan, taking into account the implementation of all measures that guarantee the safety of people. The plan must contain: a diagram of the object being repaired with the location of the repair work and an indication of their volume; a list of mechanisms, devices and tools permitted for use for repair work; surname list and arrangement of workers admitted to repair work; a complete list of measures to ensure the safe conduct of work, agreed with the gas rescue station, and a note on their implementation. The repair plan in each individual case must be signed by the head of the workshop, the person responsible for the repair and agreed with the head of the gas facilities.
The repair manager, in addition, instructs the personnel and monitors the implementation of the Rules during the preparation and implementation of repair work.
During repairs, only portable electric lighting with a voltage of not more than 12 - 24 V and in an explosion-proof version can be used. Work related to the stay of people at height should be carried out with the help of reliable ladders, platforms, scaffolds, as well as using, if necessary, safety belts (the places where the belts are caught are indicated by the repair manager). After the repair is completed, it is necessary to immediately remove cleaning and combustible materials, their traces. Then remove the plugs, purge the gas pipeline with gas and check for leaks. All joints, set up and adjust the equipment to the specified mode.
Occupational health and safety
Information portal - Occupational health and safety. Section - Labor protection in conditions of increased danger. Gas economy. Operation of gas equipment
Ecology HANDBOOK
Information
Ignition limit
Flammability limits change significantly with the addition of certain substances that can influence the development of pre-flame chain reactions. Known substances are both expanding and narrowing the limits of ignition. [ . ]
The ignition limits are influenced by the chemical composition of the fuel and oxidizer, temperature, pressure and turbulence of the medium, the concentration and type of additives or inert diluents, and the power of the ignition source during forced ignition. The effect of fuel type on flammability limits is shown in Table 3.4.[ . ]
The highest limit is such a concentration of fuel vapor in the mixture, with an increase in which the ignition of the combustible mixture does not proceed. [ . ]
The ignition temperature, flash point, and ignition temperature limits are fire hazard indicators. In table. 22.1 these indicators are presented for some technical products. [ . ]
The wider the ignition zone and the lower the lower concentration limit of ignition, the more dangerous the fumigant during storage and use. .[ . ]
Its ignition temperature is 290 ° C. The lower and upper limits of the explosive concentration of hydrogen sulfide in the air are 4 and 45.5 vol., respectively. %. Hydrogen sulfide is heavier than air, its relative density is 1.17. With the manifestations of hydrogen sulfide, explosions and fires are possible, which can spread over a vast territory and cause numerous victims and great losses. The presence of hydrogen sulfide leads to a dangerous destruction of the drilling tool and drilling equipment and causes their intense corrosion cracking, as well as corrosion of the cement stone. Hydrogen sulfide is very aggressive to clay drilling fluids in formation waters and gases. [ . ]
The ignition delay period of diesel fuel is measured by the cetane number. The cetane number of diesel fuel is the percentage (by volume) content of cetane (n. hexadecane) of a mixture with (-methylnaphthalene, which is equivalent to the test fuel in terms of engine hardness. taken as a standard within the limits of the ignition delay of the fuel (respectively 100 and 0 units).Mixtures of cetane with a-methylnaphthalene in different ratios have different flammability.
Hydrogen and acetylene have the widest flammability limits. Hydrocarbon mixtures of various compositions have close ignition limits. [ . ]
Tests of the engine with ignition by a finely focused laser beam generating plasma cores have shown that in this case the increase in pressure in the combustion chamber is more intense, the ignition limits are expanded, and the power and economic performance of the engine are improved.[ . ]
The values of the temperature limits of ignition of substances are used in the calculation of fire and explosion-proof modes of operation of technological equipment, in the assessment of emergency situations associated with spills of flammable liquids, as well as for the calculation of the concentration limits of ignition. [ . ]
The lower concentration limit of ignition is the minimum concentration of fumigant vapor in the air, at which the vapor is ignited by an open flame or an electric spark. [ . ]
The expansion of the concentration limits of ignition creates the prerequisites for ensuring stable operation of the engine on lean mixtures. [ . ]
However, it must not be overlooked that the ignition limits are determined under static conditions, i.e., in a stationary environment. As a result, they1 do not characterize the stability of combustion in the flow and do not reflect the stabilizing ability of the burner. In other words, the same heavily ballasted gas can be successfully burned in a gas burner that stabilizes combustion well, while in another burner such an attempt may be unsuccessful. .[ . ]
With an increase in the turbulence of the combustible mixture, the ignition limits expand if the characteristics of the turbulence are such that they intensify the transfer of heat and active products in the reaction zone. The ignition limits can narrow if the turbulence of the mixture, due to the intensive removal of heat and active products from the reaction zone, causes cooling and a decrease in the rate of chemical transformations. [ . ]
With a decrease in the molecular weight of hydrocarbons, the ignition limits expand. [ . ]
In addition to the concentration limits, there are also temperature limits (lower and upper) of ignition, which are understood to mean such temperatures of a substance or material at which its saturated combustible vapors form concentrations in an oxidizing environment equal to the lower and upper concentration limits of flame propagation, respectively. ]
An oil spill resulting from the destruction of a tank(s), without igniting the oil. Represents the least danger to the environment and personnel if the oil does not spread beyond the dike. When the embankment breaks as a result of the hydrodynamic impact of the flowing oil, pollution of the main components of the environment on a significant scale is possible.[ . ]
The second condition is the existence of concentration limits beyond which neither ignition nor propagation of the combustion zone at a given pressure is possible.[ . ]
There are upper (higher) and lower (lower) concentration limits of ignition. [ . ]
Chemical properties. Flash point (in open cup) 0°; limits of ignition in air - 3-17 about. %.[ . ]
During combustion in engines with spark ignition, the concentration limits of ignition of the mixture do not coincide with the specified limits for the onset of soot formation. Therefore, the soot content in the exhaust gas of spark-ignition engines is negligible.[ . ]
The variety of substances and materials predetermined different concentration limits of flame propagation. There are such concepts as the lower and upper concentration limits of flame propagation (ignition) - this is, respectively, the minimum and maximum fuel content in the "combustible substance - oxidizing environment" mixture, at which flame propagation through the mixture is possible at any distance from the ignition source. The concentration interval between the lower and upper limits is called the area of \u200b\u200bflame propagation (ignition). [ . ]
An increase in the initial temperature and pressure of the combustible mixture leads to an expansion of the ignition limits, which is explained by an increase in the rate of reactions of pre-flame transformations. [ . ]
With an increase in heat capacity, thermal conductivity and concentration of inert diluents, the ignition limits expand. [ . ]
The flammability of vapors (or gases) is characterized by the lower and upper concentration limits of ignition and the concentration zone of ignition. [ . ]
The level of measured temperatures along the axis and periphery of the loophole (Fig. 6-15, b) is less than the ignition temperature of the mixture of natural gas with air, equal to 630-680 ° C, and only at the outlet of the loophole, in its conical section, does the temperature reach 680-700 ° С, i.e., the ignition zone is located here. A significant increase in temperature is observed outside the embrasure at a distance of (1.0-1.6) Vgun.[ . ]
The fire hazard during gasification works increases significantly when the fumigant consumption rate per 1 m3 is within the ignition concentration zone. [ . ]
On fig. 2.21 shows the maximum pressure values during the explosion of the mass Mg = 15 tons of superheated gasoline. In this case, the flame speed varied within: 103.4-158.0 m/s, which corresponds to the minimum and maximum cluttered spaces at the site of ignition of the mixture. An explosion of such an amount of overheated gasoline (accident type 1 according to scenario A) is possible during cold destruction of tanks K-101 or K-102. The frequency of such an event is 1.3 10 7 year-1, so it is unlikely.[ . ]
The disadvantage of the considered process is a long-range torch spraying paste-like precipitation at a small opening angle, which leads to a breakthrough of unburned particles outside the cyclone reactor and requires the construction of an afterburner. In addition, the combustion products of the organic part of the sediments do not participate in the process of initial heat treatment - drying and heating to the ignition temperature; for this, additional fuel is consumed, and the temperature of the exhaust gases exceeds that necessary for the complete oxidation of organic substances. [ . ]
As a rule, organic solvents are flammable, their vapors form explosive mixtures with air. Degree of flammability of solvents Characterized by flash point and ignition limits. In order to avoid an explosion, it is necessary to maintain the concentration of solvent vapors in the air below the lower flammable limit. [ . ]
Combustible gases, vapors of flammable liquids and combustible dust under certain conditions form explosive mixtures with air. Distinguish between lower and upper explosive concentration limits, beyond which mixtures are not explosive. These limits vary depending on the power and characteristics of the ignition source, the temperature and pressure of the mixture, the speed of propagation of the flame, the content of inert substances. [ . ]
Combustion stops when one of the following conditions is met: elimination of a combustible substance from the combustion zone or a decrease in its concentration; reducing the percentage of oxygen in the combustion zone to the limits at which combustion is impossible; lowering the temperature of the combustible mixture to a temperature below the ignition temperature. [ . ]
In addition, the formation of fireballs or the burning of drifting gas clouds may result in the death of all people located on the territory of the facility (up to 4 people working in a shift), as well as the defeat of people outside the gas filling station. Moreover, the number of victims when they enter the affected area of the road will primarily depend on the intensity of traffic. People traveling on a highway can only be harmed if a fireball occurs or a drifting cloud ignites. Moreover, when a cloud burns, damage in the area of \u200b\u200broads is possible provided that it ignited not on the drift path, but when vehicles hit it. Also, the risk indicators are significantly affected by the professional and emergency response training of personnel.[ . ]
Dusts of many solid combustible substances suspended in air form flammable mixtures with it. The minimum concentration of dust in the air at which it ignites is called the lower concentration limit of dust ignition. The concept of an upper flammable limit for dust does not apply, since it is not possible to create very high concentrations of dust in suspension. Information on the lower concentration limit of ignition (LEL) of some dusts is presented in Table. 22.2.[ . ]
In some refineries and petrochemical plants, the amount of discharged gases can sometimes reach 10,000-15,000 m3/h. Let us assume that within five minutes 1000 m3 of gases will be discharged, in which the lower concentration limit of ignition is about 2% (vol.) (which corresponds to the explosive characteristic of most gases from oil refining and petrochemical processes). Such an amount of gas, mixed with the surrounding air, can create an explosive atmosphere of about 50,000 m3 in a short period of time. If we assume that the explosive cloud is located so that its average height is about 10 m, then the area of the cloud will be 5000 m2 or cover about 0.5 ha of the surface. It is highly probable that some kind of source of ignition may appear in such an area and then a powerful explosion will occur in this vast territory. There have been such cases. Therefore, in order to prevent an explosion, all emissions must be collected, preventing them from spreading in the atmosphere and either disposed of or burned. [ . ]
Specifications have been developed for Universine “B”. According to the conclusions about the fire and toxic properties, universin “B” belongs to class IV products and is considered a low-hazard and low-toxic compound. It is a combustible substance having an ignition temperature of 209°C and an autoignition temperature of 303°C. Temperature limits of vapor explosion: lower 100 °С, upper 180 °С. The main physical properties of universin “B” are given below.[ . ]
Let us evaluate the fire hazard (fire hazard) of various substances and materials, taking into account their state of aggregation (solid, liquid or gaseous). The main indicators of fire danger are the autoignition temperature and the concentration limits of ignition. [ . ]
Wastes from solvent gasolines, extractants, petroleum ether, which are narrow low-boiling fractions of direct distillation of oil, have a boiling point of 30-70 ° C, a flash point of -17 ° C, an autoignition temperature of 224-350 ° C, a lower concentration limit of ignition ( NKP) 1.1%, upper (VKP) 5.4%. [ . ]
The design of the neutralizer must ensure the necessary residence time of the processed gases in the apparatus at a temperature that guarantees the possibility of achieving a given degree of their neutralization (neutralization). The residence time is usually 0.1-0.5 s (sometimes up to 1 s), the operating temperature in most cases is oriented to the lower limit of self-ignition of the neutralized gas mixtures and exceeds the ignition temperature (Table 1.7) by 100-150 ° C. [ . ]
Venturi tubes, electrostatic filters and fabric (bag) filters are the main gas cleaning devices for converter production. Scrubbers, foamers and cyclones are usually used in combination with Venturi tubes and electrostatic precipitators. The content of combustible components in the gases entering the electrostatic precipitators must be significantly less than the lower flammability limit of the corresponding components. As a result, electrostatic precipitators cannot work in a gas exhaust system without afterburning. [ . ]
Calculations carried out in accordance with the method described above showed that a gas cloud with a high concentration is formed at the rupture site, which dissipates due to advective transport and turbulent diffusion in the atmosphere. Using the "RISK" program, the probabilities of exceeding two threshold values of concentrations were calculated: 300 mg/m3 - the maximum allowable concentration of methane in the working area and 35,000 mg/m3 - the lower limit of ignition of the methane-air mixture.[ . ]
A fairly complex gravity current is formed near the earth's surface, which contributes to the radial propagation and dispersion of LNG vapors. As an illustration of the results of numerical calculations of the dispersion of the methane-air cloud in Fig. Figure 5 shows the evolution of the vapor cloud for the most unfavorable dispersion conditions (atmospheric stability - “B” according to the Gifford-Pasquile classification, wind speed - 2 m/s) in the form of isosurfaces of the LNG vapor concentration in the air. The contours shown correspond to the upper flammable limit of LNG vapor in air (15% vol.), the lower flammable limit (5% vol.) and half the lower flammable limit (2.5% vol.).[ . ]
Natural gas futures rose during the American session
On the New York Mercantile Exchange, natural gas futures for August delivery traded at $2.768 per million Btu, up 0.58% as of this writing.
The high of the session was USD per MMBtu. At the time of writing, natural gas has found support at $2.736 and resistance at $2.832.
Futures on the USD index, which shows the ratio of the US dollar to a basket of six major currencies, fell 0.17% to trade at $94.28.
Elsewhere on the NYMEX, WTI September crude oil futures edged down 3.95% to hit $67.19 a barrel, while August fuel oil futures edged down 3.19% to hit $67.19 a barrel. to $2.0654 per gallon.
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July 25, 2018 from 10.00 to 13.00 GKU RK "Department of fire service and civil protection" will collect mercury-containing waste on the territory of the municipal defense organization "Ukhta"
Leading cause of death in children– neglect on the part of adults, incl. during the joint rest of parents with children.
July 16, 2018 fire department security on the landfill
On July 11, 2018, employees of the MU "Department for Civil Defense and Emergencies" carried out a visit to 1, 2, 3 Vodnensky dachas and the Trud SOT in order to carry out preventive measures to ensure fire safety measures.
On July 11, 2017, employees of the MU "Department for Civil Defense and Emergencies" of the administration of the municipal defense organization "Ukhta" checked the condition of fire reservoirs and fire-technical equipment.
MU “Department for Civil Defense and Emergencies” of the administration of the ICDO “Ukhta” recommends that Pfire safety rules for summer cottages
Approved by the administration of the municipal civil defense organization "Ukhta" dated June 29, 2018 No. 1453 "On the organization of the safety of people at water bodies on the territory of the municipal defense organization "Ukhta" in the summer of 2018"
On July 4, 2018, employees of the MU "Department for Civil Defense and Emergencies" went to the COT "Urozhay", Yaregsky dachas, in order to carry out preventive measures to ensure fire safety measures
Doctors advise not to rush to buy early watermelons and melons: they are often “overfed” with nitrates and growth stimulants, which can cause poisoning.
Due to the increasing number of deaths in the reservoirs of the Ukhta and Sosnogorsk districts, the Sosnogorsk section of the GIMS urges those visiting the reservoirs to BE CAREFUL AND BE CAREFUL.
The Ministry of Economy of the Komi Republic informs that the site "Project Management in the Komi Republic" has been put into commercial operation
Every year in Russia, several million people are burned due to contact with cow parsnip.
MU “Department for Civil Defense and Emergencies” of the administration of the ICGO “Ukhta” reminds parents of the need to strengthen control over children during the summer holidays
Reminds Residents of MUGO “Ukhta” on the rules of conduct at water bodies in the summer
Before the start of the swimming season and on the eve of the summer holidays, the Department of Civil Defense and Emergencies of the Administration of the Municipal Civil Defense Organization "Ukhta" reminds schoolchildren of safety precautions and rules of conduct while swimming
Before the start of the swimming season and on the eve of the summer holidays, the Department of Civil Defense and Emergencies of the Administration of the Municipal Civil Defense Organization "Ukhta" reminds parents of the need to talk with their children about the rules of behavior on the water
From June 15, 2018 to territory of MUGO "Ukhta" introduced special fire regime
The Sosnogorsk section of the GIMS of the Ministry of Emergency Situations of Russia informs that with the opening of navigation for a short period, cases of death of 12 people were recorded in the reservoirs of the Komi Republic
FBU "Avialesookhrana" has released a mobile application "Take care of the forest"
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Explosive limit of natural gas
July 25, 2018 from 10.00 to 13.00 GKU RK "Department of fire service and civil protection" will collect mercury-containing waste on the territory of the municipal defense organization "Ukhta" The main cause of death
